/*! 
 * LESS - Leaner CSS v1.5.0 
 * http://lesscss.org 
 * 
 * Copyright (c) 2009-2013, Alexis Sellier <self@cloudhead.net> 
 * Licensed under the Apache v2 License. 
 * 
 * @licence 
 */



(function (window, undefined) {//
// Stub out `require` in the browser
//
    function require(arg) {
        return window.less[arg.split('/')[1]];
    };


    if (typeof(window.less) === 'undefined' || typeof(window.less.nodeType) !== 'undefined') { window.less = {}; }
    less = window.less;
    tree = window.less.tree = {};
    less.mode = 'browser';

    var less, tree;

// Node.js does not have a header file added which defines less
    if (less === undefined) {
        less = exports;
        tree = require('./tree');
        less.mode = 'node';
    }
//
// less.js - parser
//
//    A relatively straight-forward predictive parser.
//    There is no tokenization/lexing stage, the input is parsed
//    in one sweep.
//
//    To make the parser fast enough to run in the browser, several
//    optimization had to be made:
//
//    - Matching and slicing on a huge input is often cause of slowdowns.
//      The solution is to chunkify the input into smaller strings.
//      The chunks are stored in the `chunks` var,
//      `j` holds the current chunk index, and `current` holds
//      the index of the current chunk in relation to `input`.
//      This gives us an almost 4x speed-up.
//
//    - In many cases, we don't need to match individual tokens;
//      for example, if a value doesn't hold any variables, operations
//      or dynamic references, the parser can effectively 'skip' it,
//      treating it as a literal.
//      An example would be '1px solid #000' - which evaluates to itself,
//      we don't need to know what the individual components are.
//      The drawback, of course is that you don't get the benefits of
//      syntax-checking on the CSS. This gives us a 50% speed-up in the parser,
//      and a smaller speed-up in the code-gen.
//
//
//    Token matching is done with the `$` function, which either takes
//    a terminal string or regexp, or a non-terminal function to call.
//    It also takes care of moving all the indices forwards.
//
//
    less.Parser = function Parser(env) {
        var input,       // LeSS input string
            i,           // current index in `input`
            j,           // current chunk
            temp,        // temporarily holds a chunk's state, for backtracking
            memo,        // temporarily holds `i`, when backtracking
            furthest,    // furthest index the parser has gone to
            chunks,      // chunkified input
            current,     // index of current chunk, in `input`
            parser,
            rootFilename = env && env.filename;

        // Top parser on an import tree must be sure there is one "env"
        // which will then be passed around by reference.
        if (!(env instanceof tree.parseEnv)) {
            env = new tree.parseEnv(env);
        }

        var imports = this.imports = {
            paths: env.paths || [],  // Search paths, when importing
            queue: [],               // Files which haven't been imported yet
            files: env.files,        // Holds the imported parse trees
            contents: env.contents,  // Holds the imported file contents
            mime:  env.mime,         // MIME type of .less files
            error: null,             // Error in parsing/evaluating an import
            push: function (path, currentFileInfo, importOptions, callback) {
                var parserImports = this;
                this.queue.push(path);

                var fileParsedFunc = function (e, root, fullPath) {
                    parserImports.queue.splice(parserImports.queue.indexOf(path), 1); // Remove the path from the queue

                    var importedPreviously = fullPath in parserImports.files || fullPath === rootFilename;

                    parserImports.files[fullPath] = root;                        // Store the root

                    if (e && !parserImports.error) { parserImports.error = e; }

                    callback(e, root, importedPreviously, fullPath);
                };

                if (less.Parser.importer) {
                    less.Parser.importer(path, currentFileInfo, fileParsedFunc, env);
                } else {
                    less.Parser.fileLoader(path, currentFileInfo, function(e, contents, fullPath, newFileInfo) {
                        if (e) {fileParsedFunc(e); return;}

                        var newEnv = new tree.parseEnv(env);

                        newEnv.currentFileInfo = newFileInfo;
                        newEnv.processImports = false;
                        newEnv.contents[fullPath] = contents;

                        if (currentFileInfo.reference || importOptions.reference) {
                            newFileInfo.reference = true;
                        }

                        if (importOptions.inline) {
                            fileParsedFunc(null, contents, fullPath);
                        } else {
                            new(less.Parser)(newEnv).parse(contents, function (e, root) {
                                fileParsedFunc(e, root, fullPath);
                            });
                        }
                    }, env);
                }
            }
        };

        function save()    { temp = chunks[j], memo = i, current = i; }
        function restore() { chunks[j] = temp, i = memo, current = i; }

        function sync() {
            if (i > current) {
                chunks[j] = chunks[j].slice(i - current);
                current = i;
            }
        }
        function isWhitespace(c) {
            // Could change to \s?
            var code = c.charCodeAt(0);
            return code === 32 || code === 10 || code === 9;
        }
        //
        // Parse from a token, regexp or string, and move forward if match
        //
        function $(tok) {
            var match, length;

            //
            // Non-terminal
            //
            if (tok instanceof Function) {
                return tok.call(parser.parsers);
                //
                // Terminal
                //
                //     Either match a single character in the input,
                //     or match a regexp in the current chunk (chunk[j]).
                //
            } else if (typeof(tok) === 'string') {
                match = input.charAt(i) === tok ? tok : null;
                length = 1;
                sync ();
            } else {
                sync ();

                if (match = tok.exec(chunks[j])) {
                    length = match[0].length;
                } else {
                    return null;
                }
            }

            // The match is confirmed, add the match length to `i`,
            // and consume any extra white-space characters (' ' || '\n')
            // which come after that. The reason for this is that LeSS's
            // grammar is mostly white-space insensitive.
            //
            if (match) {
                skipWhitespace(length);

                if(typeof(match) === 'string') {
                    return match;
                } else {
                    return match.length === 1 ? match[0] : match;
                }
            }
        }

        function skipWhitespace(length) {
            var oldi = i, oldj = j,
                endIndex = i + chunks[j].length,
                mem = i += length;

            while (i < endIndex) {
                if (! isWhitespace(input.charAt(i))) { break; }
                i++;
            }
            chunks[j] = chunks[j].slice(length + (i - mem));
            current = i;

            if (chunks[j].length === 0 && j < chunks.length - 1) { j++; }

            return oldi !== i || oldj !== j;
        }

        function expect(arg, msg) {
            var result = $(arg);
            if (! result) {
                error(msg || (typeof(arg) === 'string' ? "expected '" + arg + "' got '" + input.charAt(i) + "'"
                    : "unexpected token"));
            } else {
                return result;
            }
        }

        function error(msg, type) {
            var e = new Error(msg);
            e.index = i;
            e.type = type || 'Syntax';
            throw e;
        }

        // Same as $(), but don't change the state of the parser,
        // just return the match.
        function peek(tok) {
            if (typeof(tok) === 'string') {
                return input.charAt(i) === tok;
            } else {
                return tok.test(chunks[j]);
            }
        }

        function getInput(e, env) {
            if (e.filename && env.currentFileInfo.filename && (e.filename !== env.currentFileInfo.filename)) {
                return parser.imports.contents[e.filename];
            } else {
                return input;
            }
        }

        function getLocation(index, inputStream) {
            var n = index + 1,
                line = null,
                column = -1;

            while (--n >= 0 && inputStream.charAt(n) !== '\n') {
                column++;
            }

            if (typeof index === 'number') {
                line = (inputStream.slice(0, index).match(/\n/g) || "").length;
            }

            return {
                line: line,
                column: column
            };
        }

        function getDebugInfo(index, inputStream, env) {
            var filename = env.currentFileInfo.filename;
            if(less.mode !== 'browser' && less.mode !== 'rhino') {
                filename = require('path').resolve(filename);
            }

            return {
                lineNumber: getLocation(index, inputStream).line + 1,
                fileName: filename
            };
        }

        function LessError(e, env) {
            var input = getInput(e, env),
                loc = getLocation(e.index, input),
                line = loc.line,
                col  = loc.column,
                callLine = e.call && getLocation(e.call, input).line,
                lines = input.split('\n');

            this.type = e.type || 'Syntax';
            this.message = e.message;
            this.filename = e.filename || env.currentFileInfo.filename;
            this.index = e.index;
            this.line = typeof(line) === 'number' ? line + 1 : null;
            this.callLine = callLine + 1;
            this.callExtract = lines[callLine];
            this.stack = e.stack;
            this.column = col;
            this.extract = [
                lines[line - 1],
                lines[line],
                lines[line + 1]
            ];
        }

        LessError.prototype = new Error();
        LessError.prototype.constructor = LessError;

        this.env = env = env || {};

        // The optimization level dictates the thoroughness of the parser,
        // the lower the number, the less nodes it will create in the tree.
        // This could matter for debugging, or if you want to access
        // the individual nodes in the tree.
        this.optimization = ('optimization' in this.env) ? this.env.optimization : 1;

        //
        // The Parser
        //
        return parser = {

            imports: imports,
            //
            // Parse an input string into an abstract syntax tree,
            // call `callback` when done.
            //
            parse: function (str, callback) {
                var root, line, lines, error = null;

                i = j = current = furthest = 0;
                input = str.replace(/\r\n/g, '\n');

                // Remove potential UTF Byte Order Mark
                input = input.replace(/^\uFEFF/, '');

                parser.imports.contents[env.currentFileInfo.filename] = input;

                // Split the input into chunks.
                chunks = (function (chunks) {
                    var j = 0,
                        skip = /(?:@\{[\w-]+\}|[^"'`\{\}\/\(\)\\])+/g,
                        comment = /\/\*(?:[^*]|\*+[^\/*])*\*+\/|\/\/.*/g,
                        string = /"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'|`((?:[^`]|\\.)*)`/g,
                        level = 0,
                        match,
                        chunk = chunks[0],
                        inParam;

                    for (var i = 0, c, cc; i < input.length;) {
                        skip.lastIndex = i;
                        if (match = skip.exec(input)) {
                            if (match.index === i) {
                                i += match[0].length;
                                chunk.push(match[0]);
                            }
                        }
                        c = input.charAt(i);
                        comment.lastIndex = string.lastIndex = i;

                        if (match = string.exec(input)) {
                            if (match.index === i) {
                                i += match[0].length;
                                chunk.push(match[0]);
                                continue;
                            }
                        }

                        if (!inParam && c === '/') {
                            cc = input.charAt(i + 1);
                            if (cc === '/' || cc === '*') {
                                if (match = comment.exec(input)) {
                                    if (match.index === i) {
                                        i += match[0].length;
                                        chunk.push(match[0]);
                                        continue;
                                    }
                                }
                            }
                        }

                        switch (c) {
                            case '{':
                                if (!inParam) {
                                    level++;
                                    chunk.push(c);
                                    break;
                                }
                            /* falls through */
                            case '}':
                                if (!inParam) {
                                    level--;
                                    chunk.push(c);
                                    chunks[++j] = chunk = [];
                                    break;
                                }
                            /* falls through */
                            case '(':
                                if (!inParam) {
                                    inParam = true;
                                    chunk.push(c);
                                    break;
                                }
                            /* falls through */
                            case ')':
                                if (inParam) {
                                    inParam = false;
                                    chunk.push(c);
                                    break;
                                }
                            /* falls through */
                            default:
                                chunk.push(c);
                        }

                        i++;
                    }
                    if (level !== 0) {
                        error = new(LessError)({
                            index: i-1,
                            type: 'Parse',
                            message: (level > 0) ? "missing closing `}`" : "missing opening `{`",
                            filename: env.currentFileInfo.filename
                        }, env);
                    }

                    return chunks.map(function (c) { return c.join(''); });
                })([[]]);

                if (error) {
                    return callback(new(LessError)(error, env));
                }

                // Start with the primary rule.
                // The whole syntax tree is held under a Ruleset node,
                // with the `root` property set to true, so no `{}` are
                // output. The callback is called when the input is parsed.
                try {
                    root = new(tree.Ruleset)([], $(this.parsers.primary));
                    root.root = true;
                    root.firstRoot = true;
                } catch (e) {
                    return callback(new(LessError)(e, env));
                }

                root.toCSS = (function (evaluate) {
                    return function (options, variables) {
                        options = options || {};
                        var evaldRoot,
                            css,
                            evalEnv = new tree.evalEnv(options);

                        //
                        // Allows setting variables with a hash, so:
                        //
                        //   `{ color: new(tree.Color)('#f01') }` will become:
                        //
                        //   new(tree.Rule)('@color',
                        //     new(tree.Value)([
                        //       new(tree.Expression)([
                        //         new(tree.Color)('#f01')
                        //       ])
                        //     ])
                        //   )
                        //
                        if (typeof(variables) === 'object' && !Array.isArray(variables)) {
                            variables = Object.keys(variables).map(function (k) {
                                var value = variables[k];

                                if (! (value instanceof tree.Value)) {
                                    if (! (value instanceof tree.Expression)) {
                                        value = new(tree.Expression)([value]);
                                    }
                                    value = new(tree.Value)([value]);
                                }
                                return new(tree.Rule)('@' + k, value, false, null, 0);
                            });
                            evalEnv.frames = [new(tree.Ruleset)(null, variables)];
                        }

                        try {
                            evaldRoot = evaluate.call(this, evalEnv);

                            new(tree.joinSelectorVisitor)()
                                .run(evaldRoot);

                            new(tree.processExtendsVisitor)()
                                .run(evaldRoot);

                            new(tree.toCSSVisitor)({compress: Boolean(options.compress)})
                                .run(evaldRoot);

                            if (options.sourceMap) {
                                evaldRoot = new tree.sourceMapOutput(
                                    {
                                        writeSourceMap: options.writeSourceMap,
                                        rootNode: evaldRoot,
                                        contentsMap: parser.imports.contents,
                                        sourceMapFilename: options.sourceMapFilename,
                                        outputFilename: options.sourceMapOutputFilename,
                                        sourceMapBasepath: options.sourceMapBasepath,
                                        sourceMapRootpath: options.sourceMapRootpath,
                                        outputSourceFiles: options.outputSourceFiles,
                                        sourceMapGenerator: options.sourceMapGenerator
                                    });
                            }

                            css = evaldRoot.toCSS({
                                compress: Boolean(options.compress),
                                dumpLineNumbers: env.dumpLineNumbers,
                                strictUnits: Boolean(options.strictUnits)});
                        } catch (e) {
                            throw new(LessError)(e, env);
                        }

                        if (options.cleancss && less.mode === 'node') {
                            return require('clean-css').process(css);
                        } else if (options.compress) {
                            return css.replace(/(^(\s)+)|((\s)+$)/g, "");
                        } else {
                            return css;
                        }
                    };
                })(root.eval);

                // If `i` is smaller than the `input.length - 1`,
                // it means the parser wasn't able to parse the whole
                // string, so we've got a parsing error.
                //
                // We try to extract a \n delimited string,
                // showing the line where the parse error occured.
                // We split it up into two parts (the part which parsed,
                // and the part which didn't), so we can color them differently.
                if (i < input.length - 1) {
                    i = furthest;
                    var loc = getLocation(i, input);
                    lines = input.split('\n');
                    line = loc.line + 1;

                    error = {
                        type: "Parse",
                        message: "Unrecognised input",
                        index: i,
                        filename: env.currentFileInfo.filename,
                        line: line,
                        column: loc.column,
                        extract: [
                            lines[line - 2],
                            lines[line - 1],
                            lines[line]
                        ]
                    };
                }

                var finish = function (e) {
                    e = error || e || parser.imports.error;

                    if (e) {
                        if (!(e instanceof LessError)) {
                            e = new(LessError)(e, env);
                        }

                        return callback(e);
                    }
                    else {
                        return callback(null, root);
                    }
                };

                if (env.processImports !== false) {
                    new tree.importVisitor(this.imports, finish)
                        .run(root);
                } else {
                    return finish();
                }
            },

            //
            // Here in, the parsing rules/functions
            //
            // The basic structure of the syntax tree generated is as follows:
            //
            //   Ruleset ->  Rule -> Value -> Expression -> Entity
            //
            // Here's some LESS code:
            //
            //    .class {
            //      color: #fff;
            //      border: 1px solid #000;
            //      width: @w + 4px;
            //      > .child {...}
            //    }
            //
            // And here's what the parse tree might look like:
            //
            //     Ruleset (Selector '.class', [
            //         Rule ("color",  Value ([Expression [Color #fff]]))
            //         Rule ("border", Value ([Expression [Dimension 1px][Keyword "solid"][Color #000]]))
            //         Rule ("width",  Value ([Expression [Operation "+" [Variable "@w"][Dimension 4px]]]))
            //         Ruleset (Selector [Element '>', '.child'], [...])
            //     ])
            //
            //  In general, most rules will try to parse a token with the `$()` function, and if the return
            //  value is truly, will return a new node, of the relevant type. Sometimes, we need to check
            //  first, before parsing, that's when we use `peek()`.
            //
            parsers: {
                //
                // The `primary` rule is the *entry* and *exit* point of the parser.
                // The rules here can appear at any level of the parse tree.
                //
                // The recursive nature of the grammar is an interplay between the `block`
                // rule, which represents `{ ... }`, the `ruleset` rule, and this `primary` rule,
                // as represented by this simplified grammar:
                //
                //     primary  →  (ruleset | rule)+
                //     ruleset  →  selector+ block
                //     block    →  '{' primary '}'
                //
                // Only at one point is the primary rule not called from the
                // block rule: at the root level.
                //
                primary: function () {
                    var node, root = [];

                    while ((node = $(this.extendRule) || $(this.mixin.definition) || $(this.rule)    ||  $(this.ruleset) ||
                        $(this.mixin.call)       || $(this.comment) ||  $(this.directive))
                        || $(/^[\s\n]+/) || $(/^;+/)) {
                        node && root.push(node);
                    }
                    return root;
                },

                // We create a Comment node for CSS comments `/* */`,
                // but keep the LeSS comments `//` silent, by just skipping
                // over them.
                comment: function () {
                    var comment;

                    if (input.charAt(i) !== '/') { return; }

                    if (input.charAt(i + 1) === '/') {
                        return new(tree.Comment)($(/^\/\/.*/), true, i, env.currentFileInfo);
                    } else if (comment = $(/^\/\*(?:[^*]|\*+[^\/*])*\*+\/\n?/)) {
                        return new(tree.Comment)(comment, false, i, env.currentFileInfo);
                    }
                },

                comments: function () {
                    var comment, comments = [];

                    while(comment = $(this.comment)) {
                        comments.push(comment);
                    }

                    return comments;
                },

                //
                // Entities are tokens which can be found inside an Expression
                //
                entities: {
                    //
                    // A string, which supports escaping " and '
                    //
                    //     "milky way" 'he\'s the one!'
                    //
                    quoted: function () {
                        var str, j = i, e, index = i;

                        if (input.charAt(j) === '~') { j++, e = true; } // Escaped strings
                        if (input.charAt(j) !== '"' && input.charAt(j) !== "'") { return; }

                        e && $('~');

                        if (str = $(/^"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'/)) {
                            return new(tree.Quoted)(str[0], str[1] || str[2], e, index, env.currentFileInfo);
                        }
                    },

                    //
                    // A catch-all word, such as:
                    //
                    //     black border-collapse
                    //
                    keyword: function () {
                        var k;

                        if (k = $(/^[_A-Za-z-][_A-Za-z0-9-]*/)) {
                            var color = tree.Color.fromKeyword(k);
                            if (color) {
                                return color;
                            }
                            return new(tree.Keyword)(k);
                        }
                    },

                    //
                    // A function call
                    //
                    //     rgb(255, 0, 255)
                    //
                    // We also try to catch IE's `alpha()`, but let the `alpha` parser
                    // deal with the details.
                    //
                    // The arguments are parsed with the `entities.arguments` parser.
                    //
                    call: function () {
                        var name, nameLC, args, alpha_ret, index = i;

                        if (! (name = /^([\w-]+|%|progid:[\w\.]+)\(/.exec(chunks[j]))) { return; }

                        name = name[1];
                        nameLC = name.toLowerCase();

                        if (nameLC === 'url') { return null; }
                        else                  { i += name.length; }

                        if (nameLC === 'alpha') {
                            alpha_ret = $(this.alpha);
                            if(typeof alpha_ret !== 'undefined') {
                                return alpha_ret;
                            }
                        }

                        $('('); // Parse the '(' and consume whitespace.

                        args = $(this.entities.arguments);

                        if (! $(')')) {
                            return;
                        }

                        if (name) { return new(tree.Call)(name, args, index, env.currentFileInfo); }
                    },
                    arguments: function () {
                        var args = [], arg;

                        while (arg = $(this.entities.assignment) || $(this.expression)) {
                            args.push(arg);
                            if (! $(',')) {
                                break;
                            }
                        }
                        return args;
                    },
                    literal: function () {
                        return $(this.entities.dimension) ||
                            $(this.entities.color) ||
                            $(this.entities.quoted) ||
                            $(this.entities.unicodeDescriptor);
                    },

                    // Assignments are argument entities for calls.
                    // They are present in ie filter properties as shown below.
                    //
                    //     filter: progid:DXImageTransform.Microsoft.Alpha( *opacity=50* )
                    //

                    assignment: function () {
                        var key, value;
                        if ((key = $(/^\w+(?=\s?=)/i)) && $('=') && (value = $(this.entity))) {
                            return new(tree.Assignment)(key, value);
                        }
                    },

                    //
                    // Parse url() tokens
                    //
                    // We use a specific rule for urls, because they don't really behave like
                    // standard function calls. The difference is that the argument doesn't have
                    // to be enclosed within a string, so it can't be parsed as an Expression.
                    //
                    url: function () {
                        var value;

                        if (input.charAt(i) !== 'u' || !$(/^url\(/)) {
                            return;
                        }

                        value = $(this.entities.quoted)  || $(this.entities.variable) ||
                            $(/^(?:(?:\\[\(\)'"])|[^\(\)'"])+/) || "";

                        expect(')');

                        /*jshint eqnull:true */
                        return new(tree.URL)((value.value != null || value instanceof tree.Variable)
                            ? value : new(tree.Anonymous)(value), env.currentFileInfo);
                    },

                    //
                    // A Variable entity, such as `@fink`, in
                    //
                    //     width: @fink + 2px
                    //
                    // We use a different parser for variable definitions,
                    // see `parsers.variable`.
                    //
                    variable: function () {
                        var name, index = i;

                        if (input.charAt(i) === '@' && (name = $(/^@@?[\w-]+/))) {
                            return new(tree.Variable)(name, index, env.currentFileInfo);
                        }
                    },

                    // A variable entity useing the protective {} e.g. @{var}
                    variableCurly: function () {
                        var curly, index = i;

                        if (input.charAt(i) === '@' && (curly = $(/^@\{([\w-]+)\}/))) {
                            return new(tree.Variable)("@" + curly[1], index, env.currentFileInfo);
                        }
                    },

                    //
                    // A Hexadecimal color
                    //
                    //     #4F3C2F
                    //
                    // `rgb` and `hsl` colors are parsed through the `entities.call` parser.
                    //
                    color: function () {
                        var rgb;

                        if (input.charAt(i) === '#' && (rgb = $(/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/))) {
                            return new(tree.Color)(rgb[1]);
                        }
                    },

                    //
                    // A Dimension, that is, a number and a unit
                    //
                    //     0.5em 95%
                    //
                    dimension: function () {
                        var value, c = input.charCodeAt(i);
                        //Is the first char of the dimension 0-9, '.', '+' or '-'
                        if ((c > 57 || c < 43) || c === 47 || c == 44) {
                            return;
                        }

                        if (value = $(/^([+-]?\d*\.?\d+)(%|[a-z]+)?/)) {
                            return new(tree.Dimension)(value[1], value[2]);
                        }
                    },

                    //
                    // A unicode descriptor, as is used in unicode-range
                    //
                    // U+0??  or U+00A1-00A9
                    //
                    unicodeDescriptor: function () {
                        var ud;

                        if (ud = $(/^U\+[0-9a-fA-F?]+(\-[0-9a-fA-F?]+)?/)) {
                            return new(tree.UnicodeDescriptor)(ud[0]);
                        }
                    },

                    //
                    // JavaScript code to be evaluated
                    //
                    //     `window.location.href`
                    //
                    javascript: function () {
                        var str, j = i, e;

                        if (input.charAt(j) === '~') { j++; e = true; } // Escaped strings
                        if (input.charAt(j) !== '`') { return; }
                        if (env.javascriptEnabled !== undefined && !env.javascriptEnabled) {
                            error("You are using JavaScript, which has been disabled.");
                        }

                        if (e) { $('~'); }

                        if (str = $(/^`([^`]*)`/)) {
                            return new(tree.JavaScript)(str[1], i, e);
                        }
                    }
                },

                //
                // The variable part of a variable definition. Used in the `rule` parser
                //
                //     @fink:
                //
                variable: function () {
                    var name;

                    if (input.charAt(i) === '@' && (name = $(/^(@[\w-]+)\s*:/))) { return name[1]; }
                },

                //
                // extend syntax - used to extend selectors
                //
                extend: function(isRule) {
                    var elements, e, index = i, option, extendList = [];

                    if (!$(isRule ? /^&:extend\(/ : /^:extend\(/)) { return; }

                    do {
                        option = null;
                        elements = [];
                        while (true) {
                            option = $(/^(all)(?=\s*(\)|,))/);
                            if (option) { break; }
                            e = $(this.element);
                            if (!e) { break; }
                            elements.push(e);
                        }

                        option = option && option[1];

                        extendList.push(new(tree.Extend)(new(tree.Selector)(elements), option, index));

                    } while($(","));

                    expect(/^\)/);

                    if (isRule) {
                        expect(/^;/);
                    }

                    return extendList;
                },

                //
                // extendRule - used in a rule to extend all the parent selectors
                //
                extendRule: function() {
                    return this.extend(true);
                },

                //
                // Mixins
                //
                mixin: {
                    //
                    // A Mixin call, with an optional argument list
                    //
                    //     #mixins > .square(#fff);
                    //     .rounded(4px, black);
                    //     .button;
                    //
                    // The `while` loop is there because mixins can be
                    // namespaced, but we only support the child and descendant
                    // selector for now.
                    //
                    call: function () {
                        var elements = [], e, c, args, index = i, s = input.charAt(i), important = false;

                        if (s !== '.' && s !== '#') { return; }

                        save(); // stop us absorbing part of an invalid selector

                        while (e = $(/^[#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/)) {
                            elements.push(new(tree.Element)(c, e, i, env.currentFileInfo));
                            c = $('>');
                        }
                        if ($('(')) {
                            args = this.mixin.args.call(this, true).args;
                            expect(')');
                        }

                        args = args || [];

                        if ($(this.important)) {
                            important = true;
                        }

                        if (elements.length > 0 && ($(';') || peek('}'))) {
                            return new(tree.mixin.Call)(elements, args, index, env.currentFileInfo, important);
                        }

                        restore();
                    },
                    args: function (isCall) {
                        var expressions = [], argsSemiColon = [], isSemiColonSeperated, argsComma = [], expressionContainsNamed, name, nameLoop, value, arg,
                            returner = {args:null, variadic: false};
                        while (true) {
                            if (isCall) {
                                arg = $(this.expression);
                            } else {
                                $(this.comments);
                                if (input.charAt(i) === '.' && $(/^\.{3}/)) {
                                    returner.variadic = true;
                                    if ($(";") && !isSemiColonSeperated) {
                                        isSemiColonSeperated = true;
                                    }
                                    (isSemiColonSeperated ? argsSemiColon : argsComma)
                                        .push({ variadic: true });
                                    break;
                                }
                                arg = $(this.entities.variable) || $(this.entities.literal)
                                    || $(this.entities.keyword);
                            }

                            if (!arg) {
                                break;
                            }

                            nameLoop = null;
                            if (arg.throwAwayComments) {
                                arg.throwAwayComments();
                            }
                            value = arg;
                            var val = null;

                            if (isCall) {
                                // Variable
                                if (arg.value.length == 1) {
                                    val = arg.value[0];
                                }
                            } else {
                                val = arg;
                            }

                            if (val && val instanceof tree.Variable) {
                                if ($(':')) {
                                    if (expressions.length > 0) {
                                        if (isSemiColonSeperated) {
                                            error("Cannot mix ; and , as delimiter types");
                                        }
                                        expressionContainsNamed = true;
                                    }
                                    value = expect(this.expression);
                                    nameLoop = (name = val.name);
                                } else if (!isCall && $(/^\.{3}/)) {
                                    returner.variadic = true;
                                    if ($(";") && !isSemiColonSeperated) {
                                        isSemiColonSeperated = true;
                                    }
                                    (isSemiColonSeperated ? argsSemiColon : argsComma)
                                        .push({ name: arg.name, variadic: true });
                                    break;
                                } else if (!isCall) {
                                    name = nameLoop = val.name;
                                    value = null;
                                }
                            }

                            if (value) {
                                expressions.push(value);
                            }

                            argsComma.push({ name:nameLoop, value:value });

                            if ($(',')) {
                                continue;
                            }

                            if ($(';') || isSemiColonSeperated) {

                                if (expressionContainsNamed) {
                                    error("Cannot mix ; and , as delimiter types");
                                }

                                isSemiColonSeperated = true;

                                if (expressions.length > 1) {
                                    value = new(tree.Value)(expressions);
                                }
                                argsSemiColon.push({ name:name, value:value });

                                name = null;
                                expressions = [];
                                expressionContainsNamed = false;
                            }
                        }

                        returner.args = isSemiColonSeperated ? argsSemiColon : argsComma;
                        return returner;
                    },
                    //
                    // A Mixin definition, with a list of parameters
                    //
                    //     .rounded (@radius: 2px, @color) {
                    //        ...
                    //     }
                    //
                    // Until we have a finer grained state-machine, we have to
                    // do a look-ahead, to make sure we don't have a mixin call.
                    // See the `rule` function for more information.
                    //
                    // We start by matching `.rounded (`, and then proceed on to
                    // the argument list, which has optional default values.
                    // We store the parameters in `params`, with a `value` key,
                    // if there is a value, such as in the case of `@radius`.
                    //
                    // Once we've got our params list, and a closing `)`, we parse
                    // the `{...}` block.
                    //
                    definition: function () {
                        var name, params = [], match, ruleset, cond, variadic = false;
                        if ((input.charAt(i) !== '.' && input.charAt(i) !== '#') ||
                            peek(/^[^{]*\}/)) {
                            return;
                        }

                        save();

                        if (match = $(/^([#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+)\s*\(/)) {
                            name = match[1];

                            var argInfo = this.mixin.args.call(this, false);
                            params = argInfo.args;
                            variadic = argInfo.variadic;

                            // .mixincall("@{a}");
                            // looks a bit like a mixin definition.. so we have to be nice and restore
                            if (!$(')')) {
                                furthest = i;
                                restore();
                            }

                            $(this.comments);

                            if ($(/^when/)) { // Guard
                                cond = expect(this.conditions, 'expected condition');
                            }

                            ruleset = $(this.block);

                            if (ruleset) {
                                return new(tree.mixin.Definition)(name, params, ruleset, cond, variadic);
                            } else {
                                restore();
                            }
                        }
                    }
                },

                //
                // Entities are the smallest recognized token,
                // and can be found inside a rule's value.
                //
                entity: function () {
                    return $(this.entities.literal) || $(this.entities.variable) || $(this.entities.url) ||
                        $(this.entities.call)    || $(this.entities.keyword)  ||$(this.entities.javascript) ||
                        $(this.comment);
                },

                //
                // A Rule terminator. Note that we use `peek()` to check for '}',
                // because the `block` rule will be expecting it, but we still need to make sure
                // it's there, if ';' was ommitted.
                //
                end: function () {
                    return $(';') || peek('}');
                },

                //
                // IE's alpha function
                //
                //     alpha(opacity=88)
                //
                alpha: function () {
                    var value;

                    if (! $(/^\(opacity=/i)) { return; }
                    if (value = $(/^\d+/) || $(this.entities.variable)) {
                        expect(')');
                        return new(tree.Alpha)(value);
                    }
                },

                //
                // A Selector Element
                //
                //     div
                //     + h1
                //     #socks
                //     input[type="text"]
                //
                // Elements are the building blocks for Selectors,
                // they are made out of a `Combinator` (see combinator rule),
                // and an element name, such as a tag a class, or `*`.
                //
                element: function () {
                    var e, c, v;

                    c = $(this.combinator);

                    e = $(/^(?:\d+\.\d+|\d+)%/) || $(/^(?:[.#]?|:*)(?:[\w-]|[^\x00-\x9f]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/) ||
                        $('*') || $('&') || $(this.attribute) || $(/^\([^()@]+\)/) || $(/^[\.#](?=@)/) || $(this.entities.variableCurly);

                    if (! e) {
                        if ($('(')) {
                            if ((v = ($(this.selector))) &&
                                $(')')) {
                                e = new(tree.Paren)(v);
                            }
                        }
                    }

                    if (e) { return new(tree.Element)(c, e, i, env.currentFileInfo); }
                },

                //
                // Combinators combine elements together, in a Selector.
                //
                // Because our parser isn't white-space sensitive, special care
                // has to be taken, when parsing the descendant combinator, ` `,
                // as it's an empty space. We have to check the previous character
                // in the input, to see if it's a ` ` character. More info on how
                // we deal with this in *combinator.js*.
                //
                combinator: function () {
                    var c = input.charAt(i);

                    if (c === '>' || c === '+' || c === '~' || c === '|') {
                        i++;
                        while (input.charAt(i).match(/\s/)) { i++; }
                        return new(tree.Combinator)(c);
                    } else if (input.charAt(i - 1).match(/\s/)) {
                        return new(tree.Combinator)(" ");
                    } else {
                        return new(tree.Combinator)(null);
                    }
                },
                //
                // A CSS selector (see selector below)
                // with less extensions e.g. the ability to extend and guard
                //
                lessSelector: function () {
                    return this.selector(true);
                },
                //
                // A CSS Selector
                //
                //     .class > div + h1
                //     li a:hover
                //
                // Selectors are made out of one or more Elements, see above.
                //
                selector: function (isLess) {
                    var e, elements = [], c, extend, extendList = [], when, condition;

                    while ((isLess && (extend = $(this.extend))) || (isLess && (when = $(/^when/))) || (e = $(this.element))) {
                        if (when) {
                            condition = expect(this.conditions, 'expected condition');
                        } else if (condition) {
                            error("CSS guard can only be used at the end of selector");
                        } else if (extend) {
                            extendList.push.apply(extendList, extend);
                        } else {
                            if (extendList.length) {
                                error("Extend can only be used at the end of selector");
                            }
                            c = input.charAt(i);
                            elements.push(e);
                            e = null;
                        }
                        if (c === '{' || c === '}' || c === ';' || c === ',' || c === ')') {
                            break;
                        }
                    }

                    if (elements.length > 0) { return new(tree.Selector)(elements, extendList, condition, i, env.currentFileInfo); }
                    if (extendList.length) { error("Extend must be used to extend a selector, it cannot be used on its own"); }
                },
                attribute: function () {
                    var key, val, op;

                    if (! $('[')) { return; }

                    if (!(key = $(this.entities.variableCurly))) {
                        key = expect(/^(?:[_A-Za-z0-9-\*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
                    }

                    if ((op = $(/^[|~*$^]?=/))) {
                        val = $(this.entities.quoted) || $(/^[0-9]+%/) || $(/^[\w-]+/) || $(this.entities.variableCurly);
                    }

                    expect(']');

                    return new(tree.Attribute)(key, op, val);
                },

                //
                // The `block` rule is used by `ruleset` and `mixin.definition`.
                // It's a wrapper around the `primary` rule, with added `{}`.
                //
                block: function () {
                    var content;
                    if ($('{') && (content = $(this.primary)) && $('}')) {
                        return content;
                    }
                },

                //
                // div, .class, body > p {...}
                //
                ruleset: function () {
                    var selectors = [], s, rules, debugInfo;

                    save();

                    if (env.dumpLineNumbers) {
                        debugInfo = getDebugInfo(i, input, env);
                    }

                    while (s = $(this.lessSelector)) {
                        selectors.push(s);
                        $(this.comments);
                        if (! $(',')) { break; }
                        if (s.condition) {
                            error("Guards are only currently allowed on a single selector.");
                        }
                        $(this.comments);
                    }

                    if (selectors.length > 0 && (rules = $(this.block))) {
                        var ruleset = new(tree.Ruleset)(selectors, rules, env.strictImports);
                        if (env.dumpLineNumbers) {
                            ruleset.debugInfo = debugInfo;
                        }
                        return ruleset;
                    } else {
                        // Backtrack
                        furthest = i;
                        restore();
                    }
                },
                rule: function (tryAnonymous) {
                    var name, value, c = input.charAt(i), important, merge = false;
                    save();

                    if (c === '.' || c === '#' || c === '&') { return; }

                    if (name = $(this.variable) || $(this.ruleProperty)) {
                        // prefer to try to parse first if its a variable or we are compressing
                        // but always fallback on the other one
                        value = !tryAnonymous && (env.compress || (name.charAt(0) === '@')) ?
                            ($(this.value) || $(this.anonymousValue)) :
                            ($(this.anonymousValue) || $(this.value));


                        important = $(this.important);
                        if (name[name.length-1] === "+") {
                            merge = true;
                            name = name.substr(0, name.length - 1);
                        }

                        if (value && $(this.end)) {
                            return new (tree.Rule)(name, value, important, merge, memo, env.currentFileInfo);
                        } else {
                            furthest = i;
                            restore();
                            if (value && !tryAnonymous) {
                                return this.rule(true);
                            }
                        }
                    }
                },
                anonymousValue: function () {
                    var match;
                    if (match = /^([^@+\/'"*`(;{}-]*);/.exec(chunks[j])) {
                        i += match[0].length - 1;
                        return new(tree.Anonymous)(match[1]);
                    }
                },

                //
                // An @import directive
                //
                //     @import "lib";
                //
                // Depending on our environemnt, importing is done differently:
                // In the browser, it's an XHR request, in Node, it would be a
                // file-system operation. The function used for importing is
                // stored in `import`, which we pass to the Import constructor.
                //
                "import": function () {
                    var path, features, index = i;

                    save();

                    var dir = $(/^@import?\s+/);

                    var options = (dir ? $(this.importOptions) : null) || {};

                    if (dir && (path = $(this.entities.quoted) || $(this.entities.url))) {
                        features = $(this.mediaFeatures);
                        if ($(';')) {
                            features = features && new(tree.Value)(features);
                            return new(tree.Import)(path, features, options, index, env.currentFileInfo);
                        }
                    }

                    restore();
                },

                importOptions: function() {
                    var o, options = {}, optionName, value;

                    // list of options, surrounded by parens
                    if (! $('(')) { return null; }
                    do {
                        if (o = $(this.importOption)) {
                            optionName = o;
                            value = true;
                            switch(optionName) {
                                case "css":
                                    optionName = "less";
                                    value = false;
                                    break;
                                case "once":
                                    optionName = "multiple";
                                    value = false;
                                    break;
                            }
                            options[optionName] = value;
                            if (! $(',')) { break; }
                        }
                    } while (o);
                    expect(')');
                    return options;
                },

                importOption: function() {
                    var opt = $(/^(less|css|multiple|once|inline|reference)/);
                    if (opt) {
                        return opt[1];
                    }
                },

                mediaFeature: function () {
                    var e, p, nodes = [];

                    do {
                        if (e = ($(this.entities.keyword) || $(this.entities.variable))) {
                            nodes.push(e);
                        } else if ($('(')) {
                            p = $(this.property);
                            e = $(this.value);
                            if ($(')')) {
                                if (p && e) {
                                    nodes.push(new(tree.Paren)(new(tree.Rule)(p, e, null, null, i, env.currentFileInfo, true)));
                                } else if (e) {
                                    nodes.push(new(tree.Paren)(e));
                                } else {
                                    return null;
                                }
                            } else { return null; }
                        }
                    } while (e);

                    if (nodes.length > 0) {
                        return new(tree.Expression)(nodes);
                    }
                },

                mediaFeatures: function () {
                    var e, features = [];

                    do {
                        if (e = $(this.mediaFeature)) {
                            features.push(e);
                            if (! $(',')) { break; }
                        } else if (e = $(this.entities.variable)) {
                            features.push(e);
                            if (! $(',')) { break; }
                        }
                    } while (e);

                    return features.length > 0 ? features : null;
                },

                media: function () {
                    var features, rules, media, debugInfo;

                    if (env.dumpLineNumbers) {
                        debugInfo = getDebugInfo(i, input, env);
                    }

                    if ($(/^@media/)) {
                        features = $(this.mediaFeatures);

                        if (rules = $(this.block)) {
                            media = new(tree.Media)(rules, features, i, env.currentFileInfo);
                            if (env.dumpLineNumbers) {
                                media.debugInfo = debugInfo;
                            }
                            return media;
                        }
                    }
                },

                //
                // A CSS Directive
                //
                //     @charset "utf-8";
                //
                directive: function () {
                    var name, value, rules, nonVendorSpecificName,
                        hasBlock, hasIdentifier, hasExpression, identifier;

                    if (input.charAt(i) !== '@') { return; }

                    if (value = $(this['import']) || $(this.media)) {
                        return value;
                    }

                    save();

                    name = $(/^@[a-z-]+/);

                    if (!name) { return; }

                    nonVendorSpecificName = name;
                    if (name.charAt(1) == '-' && name.indexOf('-', 2) > 0) {
                        nonVendorSpecificName = "@" + name.slice(name.indexOf('-', 2) + 1);
                    }

                    switch(nonVendorSpecificName) {
                        case "@font-face":
                            hasBlock = true;
                            break;
                        case "@viewport":
                        case "@top-left":
                        case "@top-left-corner":
                        case "@top-center":
                        case "@top-right":
                        case "@top-right-corner":
                        case "@bottom-left":
                        case "@bottom-left-corner":
                        case "@bottom-center":
                        case "@bottom-right":
                        case "@bottom-right-corner":
                        case "@left-top":
                        case "@left-middle":
                        case "@left-bottom":
                        case "@right-top":
                        case "@right-middle":
                        case "@right-bottom":
                            hasBlock = true;
                            break;
                        case "@host":
                        case "@page":
                        case "@document":
                        case "@supports":
                        case "@keyframes":
                            hasBlock = true;
                            hasIdentifier = true;
                            break;
                        case "@namespace":
                            hasExpression = true;
                            break;
                    }

                    if (hasIdentifier) {
                        identifier = ($(/^[^{]+/) || '').trim();
                        if (identifier) {
                            name += " " + identifier;
                        }
                    }

                    if (hasBlock)
                    {
                        if (rules = $(this.block)) {
                            return new(tree.Directive)(name, rules, i, env.currentFileInfo);
                        }
                    } else {
                        if ((value = hasExpression ? $(this.expression) : $(this.entity)) && $(';')) {
                            var directive = new(tree.Directive)(name, value, i, env.currentFileInfo);
                            if (env.dumpLineNumbers) {
                                directive.debugInfo = getDebugInfo(i, input, env);
                            }
                            return directive;
                        }
                    }

                    restore();
                },

                //
                // A Value is a comma-delimited list of Expressions
                //
                //     font-family: Baskerville, Georgia, serif;
                //
                // In a Rule, a Value represents everything after the `:`,
                // and before the `;`.
                //
                value: function () {
                    var e, expressions = [];

                    while (e = $(this.expression)) {
                        expressions.push(e);
                        if (! $(',')) { break; }
                    }

                    if (expressions.length > 0) {
                        return new(tree.Value)(expressions);
                    }
                },
                important: function () {
                    if (input.charAt(i) === '!') {
                        return $(/^! *important/);
                    }
                },
                sub: function () {
                    var a, e;

                    if ($('(')) {
                        if (a = $(this.addition)) {
                            e = new(tree.Expression)([a]);
                            expect(')');
                            e.parens = true;
                            return e;
                        }
                    }
                },
                multiplication: function () {
                    var m, a, op, operation, isSpaced;
                    if (m = $(this.operand)) {
                        isSpaced = isWhitespace(input.charAt(i - 1));
                        while (!peek(/^\/[*\/]/) && (op = ($('/') || $('*')))) {
                            if (a = $(this.operand)) {
                                m.parensInOp = true;
                                a.parensInOp = true;
                                operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                                isSpaced = isWhitespace(input.charAt(i - 1));
                            } else {
                                break;
                            }
                        }
                        return operation || m;
                    }
                },
                addition: function () {
                    var m, a, op, operation, isSpaced;
                    if (m = $(this.multiplication)) {
                        isSpaced = isWhitespace(input.charAt(i - 1));
                        while ((op = $(/^[-+]\s+/) || (!isSpaced && ($('+') || $('-')))) &&
                            (a = $(this.multiplication))) {
                            m.parensInOp = true;
                            a.parensInOp = true;
                            operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                            isSpaced = isWhitespace(input.charAt(i - 1));
                        }
                        return operation || m;
                    }
                },
                conditions: function () {
                    var a, b, index = i, condition;

                    if (a = $(this.condition)) {
                        while (peek(/^,\s*(not\s*)?\(/) && $(',') && (b = $(this.condition))) {
                            condition = new(tree.Condition)('or', condition || a, b, index);
                        }
                        return condition || a;
                    }
                },
                condition: function () {
                    var a, b, c, op, index = i, negate = false;

                    if ($(/^not/)) { negate = true; }
                    expect('(');
                    if (a = $(this.addition) || $(this.entities.keyword) || $(this.entities.quoted)) {
                        if (op = $(/^(?:>=|<=|=<|[<=>])/)) {
                            if (b = $(this.addition) || $(this.entities.keyword) || $(this.entities.quoted)) {
                                c = new(tree.Condition)(op, a, b, index, negate);
                            } else {
                                error('expected expression');
                            }
                        } else {
                            c = new(tree.Condition)('=', a, new(tree.Keyword)('true'), index, negate);
                        }
                        expect(')');
                        return $(/^and/) ? new(tree.Condition)('and', c, $(this.condition)) : c;
                    }
                },

                //
                // An operand is anything that can be part of an operation,
                // such as a Color, or a Variable
                //
                operand: function () {
                    var negate, p = input.charAt(i + 1);

                    if (input.charAt(i) === '-' && (p === '@' || p === '(')) { negate = $('-'); }
                    var o = $(this.sub) || $(this.entities.dimension) ||
                        $(this.entities.color) || $(this.entities.variable) ||
                        $(this.entities.call);

                    if (negate) {
                        o.parensInOp = true;
                        o = new(tree.Negative)(o);
                    }

                    return o;
                },

                //
                // Expressions either represent mathematical operations,
                // or white-space delimited Entities.
                //
                //     1px solid black
                //     @var * 2
                //
                expression: function () {
                    var e, delim, entities = [];

                    while (e = $(this.addition) || $(this.entity)) {
                        entities.push(e);
                        // operations do not allow keyword "/" dimension (e.g. small/20px) so we support that here
                        if (!peek(/^\/[\/*]/) && (delim = $('/'))) {
                            entities.push(new(tree.Anonymous)(delim));
                        }
                    }
                    if (entities.length > 0) {
                        return new(tree.Expression)(entities);
                    }
                },
                property: function () {
                    var name;

                    if (name = $(/^(\*?-?[_a-zA-Z0-9-]+)\s*:/)) {
                        return name[1];
                    }
                },
                ruleProperty: function () {
                    var name;

                    if (name = $(/^(\*?-?[_a-zA-Z0-9-]+)\s*(\+?)\s*:/)) {
                        return name[1] + (name[2] || "");
                    }
                }
            }
        };
    };


    (function (tree) {

        tree.functions = {
            rgb: function (r, g, b) {
                return this.rgba(r, g, b, 1.0);
            },
            rgba: function (r, g, b, a) {
                var rgb = [r, g, b].map(function (c) { return scaled(c, 256); });
                a = number(a);
                return new(tree.Color)(rgb, a);
            },
            hsl: function (h, s, l) {
                return this.hsla(h, s, l, 1.0);
            },
            hsla: function (h, s, l, a) {
                function hue(h) {
                    h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
                    if      (h * 6 < 1) { return m1 + (m2 - m1) * h * 6; }
                    else if (h * 2 < 1) { return m2; }
                    else if (h * 3 < 2) { return m1 + (m2 - m1) * (2/3 - h) * 6; }
                    else                { return m1; }
                }

                h = (number(h) % 360) / 360;
                s = clamp(number(s)); l = clamp(number(l)); a = clamp(number(a));

                var m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s;
                var m1 = l * 2 - m2;

                return this.rgba(hue(h + 1/3) * 255,
                    hue(h)       * 255,
                    hue(h - 1/3) * 255,
                    a);
            },

            hsv: function(h, s, v) {
                return this.hsva(h, s, v, 1.0);
            },

            hsva: function(h, s, v, a) {
                h = ((number(h) % 360) / 360) * 360;
                s = number(s); v = number(v); a = number(a);

                var i, f;
                i = Math.floor((h / 60) % 6);
                f = (h / 60) - i;

                var vs = [v,
                    v * (1 - s),
                    v * (1 - f * s),
                    v * (1 - (1 - f) * s)];
                var perm = [[0, 3, 1],
                    [2, 0, 1],
                    [1, 0, 3],
                    [1, 2, 0],
                    [3, 1, 0],
                    [0, 1, 2]];

                return this.rgba(vs[perm[i][0]] * 255,
                    vs[perm[i][1]] * 255,
                    vs[perm[i][2]] * 255,
                    a);
            },

            hue: function (color) {
                return new(tree.Dimension)(Math.round(color.toHSL().h));
            },
            saturation: function (color) {
                return new(tree.Dimension)(Math.round(color.toHSL().s * 100), '%');
            },
            lightness: function (color) {
                return new(tree.Dimension)(Math.round(color.toHSL().l * 100), '%');
            },
            hsvhue: function(color) {
                return new(tree.Dimension)(Math.round(color.toHSV().h));
            },
            hsvsaturation: function (color) {
                return new(tree.Dimension)(Math.round(color.toHSV().s * 100), '%');
            },
            hsvvalue: function (color) {
                return new(tree.Dimension)(Math.round(color.toHSV().v * 100), '%');
            },
            red: function (color) {
                return new(tree.Dimension)(color.rgb[0]);
            },
            green: function (color) {
                return new(tree.Dimension)(color.rgb[1]);
            },
            blue: function (color) {
                return new(tree.Dimension)(color.rgb[2]);
            },
            alpha: function (color) {
                return new(tree.Dimension)(color.toHSL().a);
            },
            luma: function (color) {
                return new(tree.Dimension)(Math.round(color.luma() * color.alpha * 100), '%');
            },
            saturate: function (color, amount) {
                // filter: saturate(3.2);
                // should be kept as is, so check for color
                if (!color.rgb) {
                    return null;
                }
                var hsl = color.toHSL();

                hsl.s += amount.value / 100;
                hsl.s = clamp(hsl.s);
                return hsla(hsl);
            },
            desaturate: function (color, amount) {
                var hsl = color.toHSL();

                hsl.s -= amount.value / 100;
                hsl.s = clamp(hsl.s);
                return hsla(hsl);
            },
            lighten: function (color, amount) {
                var hsl = color.toHSL();

                hsl.l += amount.value / 100;
                hsl.l = clamp(hsl.l);
                return hsla(hsl);
            },
            darken: function (color, amount) {
                var hsl = color.toHSL();

                hsl.l -= amount.value / 100;
                hsl.l = clamp(hsl.l);
                return hsla(hsl);
            },
            fadein: function (color, amount) {
                var hsl = color.toHSL();

                hsl.a += amount.value / 100;
                hsl.a = clamp(hsl.a);
                return hsla(hsl);
            },
            fadeout: function (color, amount) {
                var hsl = color.toHSL();

                hsl.a -= amount.value / 100;
                hsl.a = clamp(hsl.a);
                return hsla(hsl);
            },
            fade: function (color, amount) {
                var hsl = color.toHSL();

                hsl.a = amount.value / 100;
                hsl.a = clamp(hsl.a);
                return hsla(hsl);
            },
            spin: function (color, amount) {
                var hsl = color.toHSL();
                var hue = (hsl.h + amount.value) % 360;

                hsl.h = hue < 0 ? 360 + hue : hue;

                return hsla(hsl);
            },
            //
            // Copyright (c) 2006-2009 Hampton Catlin, Nathan Weizenbaum, and Chris Eppstein
            // http://sass-lang.com
            //
            mix: function (color1, color2, weight) {
                if (!weight) {
                    weight = new(tree.Dimension)(50);
                }
                var p = weight.value / 100.0;
                var w = p * 2 - 1;
                var a = color1.toHSL().a - color2.toHSL().a;

                var w1 = (((w * a == -1) ? w : (w + a) / (1 + w * a)) + 1) / 2.0;
                var w2 = 1 - w1;

                var rgb = [color1.rgb[0] * w1 + color2.rgb[0] * w2,
                    color1.rgb[1] * w1 + color2.rgb[1] * w2,
                    color1.rgb[2] * w1 + color2.rgb[2] * w2];

                var alpha = color1.alpha * p + color2.alpha * (1 - p);

                return new(tree.Color)(rgb, alpha);
            },
            greyscale: function (color) {
                return this.desaturate(color, new(tree.Dimension)(100));
            },
            contrast: function (color, dark, light, threshold) {
                // filter: contrast(3.2);
                // should be kept as is, so check for color
                if (!color.rgb) {
                    return null;
                }
                if (typeof light === 'undefined') {
                    light = this.rgba(255, 255, 255, 1.0);
                }
                if (typeof dark === 'undefined') {
                    dark = this.rgba(0, 0, 0, 1.0);
                }
                //Figure out which is actually light and dark!
                if (dark.luma() > light.luma()) {
                    var t = light;
                    light = dark;
                    dark = t;
                }
                if (typeof threshold === 'undefined') {
                    threshold = 0.43;
                } else {
                    threshold = number(threshold);
                }
                if ((color.luma() * color.alpha) < threshold) {
                    return light;
                } else {
                    return dark;
                }
            },
            e: function (str) {
                return new(tree.Anonymous)(str instanceof tree.JavaScript ? str.evaluated : str);
            },
            escape: function (str) {
                return new(tree.Anonymous)(encodeURI(str.value).replace(/=/g, "%3D").replace(/:/g, "%3A").replace(/#/g, "%23").replace(/;/g, "%3B").replace(/\(/g, "%28").replace(/\)/g, "%29"));
            },
            '%': function (quoted /* arg, arg, ...*/) {
                var args = Array.prototype.slice.call(arguments, 1),
                    str = quoted.value;

                for (var i = 0; i < args.length; i++) {
                    /*jshint loopfunc:true */
                    str = str.replace(/%[sda]/i, function(token) {
                        var value = token.match(/s/i) ? args[i].value : args[i].toCSS();
                        return token.match(/[A-Z]$/) ? encodeURIComponent(value) : value;
                    });
                }
                str = str.replace(/%%/g, '%');
                return new(tree.Quoted)('"' + str + '"', str);
            },
            unit: function (val, unit) {
                if(!(val instanceof tree.Dimension)) {
                    throw { type: "Argument", message: "the first argument to unit must be a number" + (val instanceof tree.Operation ? ". Have you forgotten parenthesis?" : "") };
                }
                return new(tree.Dimension)(val.value, unit ? unit.toCSS() : "");
            },
            convert: function (val, unit) {
                return val.convertTo(unit.value);
            },
            round: function (n, f) {
                var fraction = typeof(f) === "undefined" ? 0 : f.value;
                return this._math(function(num) { return num.toFixed(fraction); }, null, n);
            },
            pi: function () {
                return new(tree.Dimension)(Math.PI);
            },
            mod: function(a, b) {
                return new(tree.Dimension)(a.value % b.value, a.unit);
            },
            pow: function(x, y) {
                if (typeof x === "number" && typeof y === "number") {
                    x = new(tree.Dimension)(x);
                    y = new(tree.Dimension)(y);
                } else if (!(x instanceof tree.Dimension) || !(y instanceof tree.Dimension)) {
                    throw { type: "Argument", message: "arguments must be numbers" };
                }

                return new(tree.Dimension)(Math.pow(x.value, y.value), x.unit);
            },
            _math: function (fn, unit, n) {
                if (n instanceof tree.Dimension) {
                    /*jshint eqnull:true */
                    return new(tree.Dimension)(fn(parseFloat(n.value)), unit == null ? n.unit : unit);
                } else if (typeof(n) === 'number') {
                    return fn(n);
                } else {
                    throw { type: "Argument", message: "argument must be a number" };
                }
            },
            _minmax: function (isMin, args) {
                args = Array.prototype.slice.call(args);
                switch(args.length) {
                    case 0: throw { type: "Argument", message: "one or more arguments required" };
                    case 1: return args[0];
                }
                var i, j, current, currentUnified, referenceUnified, unit,
                    order  = [], // elems only contains original argument values.
                    values = {}; // key is the unit.toString() for unified tree.Dimension values,
                // value is the index into the order array.
                for (i = 0; i < args.length; i++) {
                    current = args[i];
                    if (!(current instanceof tree.Dimension)) {
                        order.push(current);
                        continue;
                    }
                    currentUnified = current.unify();
                    unit = currentUnified.unit.toString();
                    j = values[unit];
                    if (j === undefined) {
                        values[unit] = order.length;
                        order.push(current);
                        continue;
                    }
                    referenceUnified = order[j].unify();
                    if ( isMin && currentUnified.value < referenceUnified.value ||
                        !isMin && currentUnified.value > referenceUnified.value) {
                        order[j] = current;
                    }
                }
                if (order.length == 1) {
                    return order[0];
                }
                args = order.map(function (a) { return a.toCSS(this.env); })
                    .join(this.env.compress ? "," : ", ");
                return new(tree.Anonymous)((isMin ? "min" : "max") + "(" + args + ")");
            },
            min: function () {
                return this._minmax(true, arguments);
            },
            max: function () {
                return this._minmax(false, arguments);
            },
            argb: function (color) {
                return new(tree.Anonymous)(color.toARGB());

            },
            percentage: function (n) {
                return new(tree.Dimension)(n.value * 100, '%');
            },
            color: function (n) {
                if (n instanceof tree.Quoted) {
                    var colorCandidate = n.value,
                        returnColor;
                    returnColor = tree.Color.fromKeyword(colorCandidate);
                    if (returnColor) {
                        return returnColor;
                    }
                    if (/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/.test(colorCandidate)) {
                        return new(tree.Color)(colorCandidate.slice(1));
                    }
                    throw { type: "Argument", message: "argument must be a color keyword or 3/6 digit hex e.g. #FFF" };
                } else {
                    throw { type: "Argument", message: "argument must be a string" };
                }
            },
            iscolor: function (n) {
                return this._isa(n, tree.Color);
            },
            isnumber: function (n) {
                return this._isa(n, tree.Dimension);
            },
            isstring: function (n) {
                return this._isa(n, tree.Quoted);
            },
            iskeyword: function (n) {
                return this._isa(n, tree.Keyword);
            },
            isurl: function (n) {
                return this._isa(n, tree.URL);
            },
            ispixel: function (n) {
                return this.isunit(n, 'px');
            },
            ispercentage: function (n) {
                return this.isunit(n, '%');
            },
            isem: function (n) {
                return this.isunit(n, 'em');
            },
            isunit: function (n, unit) {
                return (n instanceof tree.Dimension) && n.unit.is(unit.value || unit) ? tree.True : tree.False;
            },
            _isa: function (n, Type) {
                return (n instanceof Type) ? tree.True : tree.False;
            },

            /* Blending modes */

            multiply: function(color1, color2) {
                var r = color1.rgb[0] * color2.rgb[0] / 255;
                var g = color1.rgb[1] * color2.rgb[1] / 255;
                var b = color1.rgb[2] * color2.rgb[2] / 255;
                return this.rgb(r, g, b);
            },
            screen: function(color1, color2) {
                var r = 255 - (255 - color1.rgb[0]) * (255 - color2.rgb[0]) / 255;
                var g = 255 - (255 - color1.rgb[1]) * (255 - color2.rgb[1]) / 255;
                var b = 255 - (255 - color1.rgb[2]) * (255 - color2.rgb[2]) / 255;
                return this.rgb(r, g, b);
            },
            overlay: function(color1, color2) {
                var r = color1.rgb[0] < 128 ? 2 * color1.rgb[0] * color2.rgb[0] / 255 : 255 - 2 * (255 - color1.rgb[0]) * (255 - color2.rgb[0]) / 255;
                var g = color1.rgb[1] < 128 ? 2 * color1.rgb[1] * color2.rgb[1] / 255 : 255 - 2 * (255 - color1.rgb[1]) * (255 - color2.rgb[1]) / 255;
                var b = color1.rgb[2] < 128 ? 2 * color1.rgb[2] * color2.rgb[2] / 255 : 255 - 2 * (255 - color1.rgb[2]) * (255 - color2.rgb[2]) / 255;
                return this.rgb(r, g, b);
            },
            softlight: function(color1, color2) {
                var t = color2.rgb[0] * color1.rgb[0] / 255;
                var r = t + color1.rgb[0] * (255 - (255 - color1.rgb[0]) * (255 - color2.rgb[0]) / 255 - t) / 255;
                t = color2.rgb[1] * color1.rgb[1] / 255;
                var g = t + color1.rgb[1] * (255 - (255 - color1.rgb[1]) * (255 - color2.rgb[1]) / 255 - t) / 255;
                t = color2.rgb[2] * color1.rgb[2] / 255;
                var b = t + color1.rgb[2] * (255 - (255 - color1.rgb[2]) * (255 - color2.rgb[2]) / 255 - t) / 255;
                return this.rgb(r, g, b);
            },
            hardlight: function(color1, color2) {
                var r = color2.rgb[0] < 128 ? 2 * color2.rgb[0] * color1.rgb[0] / 255 : 255 - 2 * (255 - color2.rgb[0]) * (255 - color1.rgb[0]) / 255;
                var g = color2.rgb[1] < 128 ? 2 * color2.rgb[1] * color1.rgb[1] / 255 : 255 - 2 * (255 - color2.rgb[1]) * (255 - color1.rgb[1]) / 255;
                var b = color2.rgb[2] < 128 ? 2 * color2.rgb[2] * color1.rgb[2] / 255 : 255 - 2 * (255 - color2.rgb[2]) * (255 - color1.rgb[2]) / 255;
                return this.rgb(r, g, b);
            },
            difference: function(color1, color2) {
                var r = Math.abs(color1.rgb[0] - color2.rgb[0]);
                var g = Math.abs(color1.rgb[1] - color2.rgb[1]);
                var b = Math.abs(color1.rgb[2] - color2.rgb[2]);
                return this.rgb(r, g, b);
            },
            exclusion: function(color1, color2) {
                var r = color1.rgb[0] + color2.rgb[0] * (255 - color1.rgb[0] - color1.rgb[0]) / 255;
                var g = color1.rgb[1] + color2.rgb[1] * (255 - color1.rgb[1] - color1.rgb[1]) / 255;
                var b = color1.rgb[2] + color2.rgb[2] * (255 - color1.rgb[2] - color1.rgb[2]) / 255;
                return this.rgb(r, g, b);
            },
            average: function(color1, color2) {
                var r = (color1.rgb[0] + color2.rgb[0]) / 2;
                var g = (color1.rgb[1] + color2.rgb[1]) / 2;
                var b = (color1.rgb[2] + color2.rgb[2]) / 2;
                return this.rgb(r, g, b);
            },
            negation: function(color1, color2) {
                var r = 255 - Math.abs(255 - color2.rgb[0] - color1.rgb[0]);
                var g = 255 - Math.abs(255 - color2.rgb[1] - color1.rgb[1]);
                var b = 255 - Math.abs(255 - color2.rgb[2] - color1.rgb[2]);
                return this.rgb(r, g, b);
            },
            tint: function(color, amount) {
                return this.mix(this.rgb(255,255,255), color, amount);
            },
            shade: function(color, amount) {
                return this.mix(this.rgb(0, 0, 0), color, amount);
            },
            extract: function(values, index) {
                index = index.value - 1; // (1-based index)       
                // handle non-array values as an array of length 1
                // return 'undefined' if index is invalid
                return Array.isArray(values.value)
                    ? values.value[index] : Array(values)[index];
            },
            length: function(values) {
                var n = Array.isArray(values.value) ? values.value.length : 1;
                return new tree.Dimension(n);
            },

            "data-uri": function(mimetypeNode, filePathNode) {

                if (typeof window !== 'undefined') {
                    return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
                }

                var mimetype = mimetypeNode.value;
                var filePath = (filePathNode && filePathNode.value);

                var fs = require("fs"),
                    path = require("path"),
                    useBase64 = false;

                if (arguments.length < 2) {
                    filePath = mimetype;
                }

                if (this.env.isPathRelative(filePath)) {
                    if (this.currentFileInfo.relativeUrls) {
                        filePath = path.join(this.currentFileInfo.currentDirectory, filePath);
                    } else {
                        filePath = path.join(this.currentFileInfo.entryPath, filePath);
                    }
                }

                // detect the mimetype if not given
                if (arguments.length < 2) {
                    var mime;
                    try {
                        mime = require('mime');
                    } catch (ex) {
                        mime = tree._mime;
                    }

                    mimetype = mime.lookup(filePath);

                    // use base 64 unless it's an ASCII or UTF-8 format
                    var charset = mime.charsets.lookup(mimetype);
                    useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
                    if (useBase64) { mimetype += ';base64'; }
                }
                else {
                    useBase64 = /;base64$/.test(mimetype);
                }

                var buf = fs.readFileSync(filePath);

                // IE8 cannot handle a data-uri larger than 32KB. If this is exceeded
                // and the --ieCompat flag is enabled, return a normal url() instead.
                var DATA_URI_MAX_KB = 32,
                    fileSizeInKB = parseInt((buf.length / 1024), 10);
                if (fileSizeInKB >= DATA_URI_MAX_KB) {

                    if (this.env.ieCompat !== false) {
                        if (!this.env.silent) {
                            console.warn("Skipped data-uri embedding of %s because its size (%dKB) exceeds IE8-safe %dKB!", filePath, fileSizeInKB, DATA_URI_MAX_KB);
                        }

                        return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
                    }
                }

                buf = useBase64 ? buf.toString('base64')
                    : encodeURIComponent(buf);

                var uri = "'data:" + mimetype + ',' + buf + "'";
                return new(tree.URL)(new(tree.Anonymous)(uri));
            },

            "svg-gradient": function(direction) {

                function throwArgumentDescriptor() {
                    throw { type: "Argument", message: "svg-gradient expects direction, start_color [start_position], [color position,]..., end_color [end_position]" };
                }

                if (arguments.length < 3) {
                    throwArgumentDescriptor();
                }
                var stops = Array.prototype.slice.call(arguments, 1),
                    gradientDirectionSvg,
                    gradientType = "linear",
                    rectangleDimension = 'x="0" y="0" width="1" height="1"',
                    useBase64 = true,
                    renderEnv = {compress: false},
                    returner,
                    directionValue = direction.toCSS(renderEnv),
                    i, color, position, positionValue, alpha;

                switch (directionValue) {
                    case "to bottom":
                        gradientDirectionSvg = 'x1="0%" y1="0%" x2="0%" y2="100%"';
                        break;
                    case "to right":
                        gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="0%"';
                        break;
                    case "to bottom right":
                        gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="100%"';
                        break;
                    case "to top right":
                        gradientDirectionSvg = 'x1="0%" y1="100%" x2="100%" y2="0%"';
                        break;
                    case "ellipse":
                    case "ellipse at center":
                        gradientType = "radial";
                        gradientDirectionSvg = 'cx="50%" cy="50%" r="75%"';
                        rectangleDimension = 'x="-50" y="-50" width="101" height="101"';
                        break;
                    default:
                        throw { type: "Argument", message: "svg-gradient direction must be 'to bottom', 'to right', 'to bottom right', 'to top right' or 'ellipse at center'" };
                }
                returner = '<?xml version="1.0" ?>' +
                    '<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100%" height="100%" viewBox="0 0 1 1" preserveAspectRatio="none">' +
                    '<' + gradientType + 'Gradient id="gradient" gradientUnits="userSpaceOnUse" ' + gradientDirectionSvg + '>';

                for (i = 0; i < stops.length; i+= 1) {
                    if (stops[i].value) {
                        color = stops[i].value[0];
                        position = stops[i].value[1];
                    } else {
                        color = stops[i];
                        position = undefined;
                    }

                    if (!(color instanceof tree.Color) || (!((i === 0 || i+1 === stops.length) && position === undefined) && !(position instanceof tree.Dimension))) {
                        throwArgumentDescriptor();
                    }
                    positionValue = position ? position.toCSS(renderEnv) : i === 0 ? "0%" : "100%";
                    alpha = color.alpha;
                    returner += '<stop offset="' + positionValue + '" stop-color="' + color.toRGB() + '"' + (alpha < 1 ? ' stop-opacity="' + alpha + '"' : '') + '/>';
                }
                returner += '</' + gradientType + 'Gradient>' +
                    '<rect ' + rectangleDimension + ' fill="url(#gradient)" /></svg>';

                if (useBase64) {
                    // only works in node, needs interface to what is supported in environment
                    try {
                        returner = new Buffer(returner).toString('base64');
                    } catch(e) {
                        useBase64 = false;
                    }
                }

                returner = "'data:image/svg+xml" + (useBase64 ? ";base64" : "") + "," + returner + "'";
                return new(tree.URL)(new(tree.Anonymous)(returner));
            }
        };

// these static methods are used as a fallback when the optional 'mime' dependency is missing
        tree._mime = {
            // this map is intentionally incomplete
            // if you want more, install 'mime' dep
            _types: {
                '.htm' : 'text/html',
                '.html': 'text/html',
                '.gif' : 'image/gif',
                '.jpg' : 'image/jpeg',
                '.jpeg': 'image/jpeg',
                '.png' : 'image/png'
            },
            lookup: function (filepath) {
                var ext = require('path').extname(filepath),
                    type = tree._mime._types[ext];
                if (type === undefined) {
                    throw new Error('Optional dependency "mime" is required for ' + ext);
                }
                return type;
            },
            charsets: {
                lookup: function (type) {
                    // assumes all text types are UTF-8
                    return type && (/^text\//).test(type) ? 'UTF-8' : '';
                }
            }
        };

        var mathFunctions = [{name:"ceil"}, {name:"floor"}, {name: "sqrt"}, {name:"abs"},
                {name:"tan", unit: ""}, {name:"sin", unit: ""}, {name:"cos", unit: ""},
                {name:"atan", unit: "rad"}, {name:"asin", unit: "rad"}, {name:"acos", unit: "rad"}],
            createMathFunction = function(name, unit) {
                return function(n) {
                    /*jshint eqnull:true */
                    if (unit != null) {
                        n = n.unify();
                    }
                    return this._math(Math[name], unit, n);
                };
            };

        for(var i = 0; i < mathFunctions.length; i++) {
            tree.functions[mathFunctions[i].name] = createMathFunction(mathFunctions[i].name, mathFunctions[i].unit);
        }

        function hsla(color) {
            return tree.functions.hsla(color.h, color.s, color.l, color.a);
        }

        function scaled(n, size) {
            if (n instanceof tree.Dimension && n.unit.is('%')) {
                return parseFloat(n.value * size / 100);
            } else {
                return number(n);
            }
        }

        function number(n) {
            if (n instanceof tree.Dimension) {
                return parseFloat(n.unit.is('%') ? n.value / 100 : n.value);
            } else if (typeof(n) === 'number') {
                return n;
            } else {
                throw {
                    error: "RuntimeError",
                    message: "color functions take numbers as parameters"
                };
            }
        }

        function clamp(val) {
            return Math.min(1, Math.max(0, val));
        }

        tree.functionCall = function(env, currentFileInfo) {
            this.env = env;
            this.currentFileInfo = currentFileInfo;
        };

        tree.functionCall.prototype = tree.functions;

    })(require('./tree'));

    (function (tree) {
        tree.colors = {
            'aliceblue':'#f0f8ff',
            'antiquewhite':'#faebd7',
            'aqua':'#00ffff',
            'aquamarine':'#7fffd4',
            'azure':'#f0ffff',
            'beige':'#f5f5dc',
            'bisque':'#ffe4c4',
            'black':'#000000',
            'blanchedalmond':'#ffebcd',
            'blue':'#0000ff',
            'blueviolet':'#8a2be2',
            'brown':'#a52a2a',
            'burlywood':'#deb887',
            'cadetblue':'#5f9ea0',
            'chartreuse':'#7fff00',
            'chocolate':'#d2691e',
            'coral':'#ff7f50',
            'cornflowerblue':'#6495ed',
            'cornsilk':'#fff8dc',
            'crimson':'#dc143c',
            'cyan':'#00ffff',
            'darkblue':'#00008b',
            'darkcyan':'#008b8b',
            'darkgoldenrod':'#b8860b',
            'darkgray':'#a9a9a9',
            'darkgrey':'#a9a9a9',
            'darkgreen':'#006400',
            'darkkhaki':'#bdb76b',
            'darkmagenta':'#8b008b',
            'darkolivegreen':'#556b2f',
            'darkorange':'#ff8c00',
            'darkorchid':'#9932cc',
            'darkred':'#8b0000',
            'darksalmon':'#e9967a',
            'darkseagreen':'#8fbc8f',
            'darkslateblue':'#483d8b',
            'darkslategray':'#2f4f4f',
            'darkslategrey':'#2f4f4f',
            'darkturquoise':'#00ced1',
            'darkviolet':'#9400d3',
            'deeppink':'#ff1493',
            'deepskyblue':'#00bfff',
            'dimgray':'#696969',
            'dimgrey':'#696969',
            'dodgerblue':'#1e90ff',
            'firebrick':'#b22222',
            'floralwhite':'#fffaf0',
            'forestgreen':'#228b22',
            'fuchsia':'#ff00ff',
            'gainsboro':'#dcdcdc',
            'ghostwhite':'#f8f8ff',
            'gold':'#ffd700',
            'goldenrod':'#daa520',
            'gray':'#808080',
            'grey':'#808080',
            'green':'#008000',
            'greenyellow':'#adff2f',
            'honeydew':'#f0fff0',
            'hotpink':'#ff69b4',
            'indianred':'#cd5c5c',
            'indigo':'#4b0082',
            'ivory':'#fffff0',
            'khaki':'#f0e68c',
            'lavender':'#e6e6fa',
            'lavenderblush':'#fff0f5',
            'lawngreen':'#7cfc00',
            'lemonchiffon':'#fffacd',
            'lightblue':'#add8e6',
            'lightcoral':'#f08080',
            'lightcyan':'#e0ffff',
            'lightgoldenrodyellow':'#fafad2',
            'lightgray':'#d3d3d3',
            'lightgrey':'#d3d3d3',
            'lightgreen':'#90ee90',
            'lightpink':'#ffb6c1',
            'lightsalmon':'#ffa07a',
            'lightseagreen':'#20b2aa',
            'lightskyblue':'#87cefa',
            'lightslategray':'#778899',
            'lightslategrey':'#778899',
            'lightsteelblue':'#b0c4de',
            'lightyellow':'#ffffe0',
            'lime':'#00ff00',
            'limegreen':'#32cd32',
            'linen':'#faf0e6',
            'magenta':'#ff00ff',
            'maroon':'#800000',
            'mediumaquamarine':'#66cdaa',
            'mediumblue':'#0000cd',
            'mediumorchid':'#ba55d3',
            'mediumpurple':'#9370d8',
            'mediumseagreen':'#3cb371',
            'mediumslateblue':'#7b68ee',
            'mediumspringgreen':'#00fa9a',
            'mediumturquoise':'#48d1cc',
            'mediumvioletred':'#c71585',
            'midnightblue':'#191970',
            'mintcream':'#f5fffa',
            'mistyrose':'#ffe4e1',
            'moccasin':'#ffe4b5',
            'navajowhite':'#ffdead',
            'navy':'#000080',
            'oldlace':'#fdf5e6',
            'olive':'#808000',
            'olivedrab':'#6b8e23',
            'orange':'#ffa500',
            'orangered':'#ff4500',
            'orchid':'#da70d6',
            'palegoldenrod':'#eee8aa',
            'palegreen':'#98fb98',
            'paleturquoise':'#afeeee',
            'palevioletred':'#d87093',
            'papayawhip':'#ffefd5',
            'peachpuff':'#ffdab9',
            'peru':'#cd853f',
            'pink':'#ffc0cb',
            'plum':'#dda0dd',
            'powderblue':'#b0e0e6',
            'purple':'#800080',
            'red':'#ff0000',
            'rosybrown':'#bc8f8f',
            'royalblue':'#4169e1',
            'saddlebrown':'#8b4513',
            'salmon':'#fa8072',
            'sandybrown':'#f4a460',
            'seagreen':'#2e8b57',
            'seashell':'#fff5ee',
            'sienna':'#a0522d',
            'silver':'#c0c0c0',
            'skyblue':'#87ceeb',
            'slateblue':'#6a5acd',
            'slategray':'#708090',
            'slategrey':'#708090',
            'snow':'#fffafa',
            'springgreen':'#00ff7f',
            'steelblue':'#4682b4',
            'tan':'#d2b48c',
            'teal':'#008080',
            'thistle':'#d8bfd8',
            'tomato':'#ff6347',
            'turquoise':'#40e0d0',
            'violet':'#ee82ee',
            'wheat':'#f5deb3',
            'white':'#ffffff',
            'whitesmoke':'#f5f5f5',
            'yellow':'#ffff00',
            'yellowgreen':'#9acd32'
        };
    })(require('./tree'));

    (function (tree) {

        tree.debugInfo = function(env, ctx, lineSeperator) {
            var result="";
            if (env.dumpLineNumbers && !env.compress) {
                switch(env.dumpLineNumbers) {
                    case 'comments':
                        result = tree.debugInfo.asComment(ctx);
                        break;
                    case 'mediaquery':
                        result = tree.debugInfo.asMediaQuery(ctx);
                        break;
                    case 'all':
                        result = tree.debugInfo.asComment(ctx) + (lineSeperator || "") + tree.debugInfo.asMediaQuery(ctx);
                        break;
                }
            }
            return result;
        };

        tree.debugInfo.asComment = function(ctx) {
            return '/* line ' + ctx.debugInfo.lineNumber + ', ' + ctx.debugInfo.fileName + ' */\n';
        };

        tree.debugInfo.asMediaQuery = function(ctx) {
            return '@media -sass-debug-info{filename{font-family:' +
                ('file://' + ctx.debugInfo.fileName).replace(/([.:/\\])/g, function (a) {
                    if (a == '\\') {
                        a = '\/';
                    }
                    return '\\' + a;
                }) +
                '}line{font-family:\\00003' + ctx.debugInfo.lineNumber + '}}\n';
        };

        tree.find = function (obj, fun) {
            for (var i = 0, r; i < obj.length; i++) {
                if (r = fun.call(obj, obj[i])) { return r; }
            }
            return null;
        };

        tree.jsify = function (obj) {
            if (Array.isArray(obj.value) && (obj.value.length > 1)) {
                return '[' + obj.value.map(function (v) { return v.toCSS(false); }).join(', ') + ']';
            } else {
                return obj.toCSS(false);
            }
        };

        tree.toCSS = function (env) {
            var strs = [];
            this.genCSS(env, {
                add: function(chunk, fileInfo, index) {
                    strs.push(chunk);
                },
                isEmpty: function () {
                    return strs.length === 0;
                }
            });
            return strs.join('');
        };

        tree.outputRuleset = function (env, output, rules) {
            output.add((env.compress ? '{' : ' {\n'));
            env.tabLevel = (env.tabLevel || 0) + 1;
            var tabRuleStr = env.compress ? '' : Array(env.tabLevel + 1).join("  "),
                tabSetStr = env.compress ? '' : Array(env.tabLevel).join("  ");
            for(var i = 0; i < rules.length; i++) {
                output.add(tabRuleStr);
                rules[i].genCSS(env, output);
                output.add(env.compress ? '' : '\n');
            }
            env.tabLevel--;
            output.add(tabSetStr + "}");
        };

    })(require('./tree'));

    (function (tree) {

        tree.Alpha = function (val) {
            this.value = val;
        };
        tree.Alpha.prototype = {
            type: "Alpha",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                if (this.value.eval) { return new tree.Alpha(this.value.eval(env)); }
                return this;
            },
            genCSS: function (env, output) {
                output.add("alpha(opacity=");

                if (this.value.genCSS) {
                    this.value.genCSS(env, output);
                } else {
                    output.add(this.value);
                }

                output.add(")");
            },
            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {

        tree.Anonymous = function (string, index, currentFileInfo, mapLines) {
            this.value = string.value || string;
            this.index = index;
            this.mapLines = mapLines;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Anonymous.prototype = {
            type: "Anonymous",
            eval: function () { return this; },
            compare: function (x) {
                if (!x.toCSS) {
                    return -1;
                }

                var left = this.toCSS(),
                    right = x.toCSS();

                if (left === right) {
                    return 0;
                }

                return left < right ? -1 : 1;
            },
            genCSS: function (env, output) {
                output.add(this.value, this.currentFileInfo, this.index, this.mapLines);
            },
            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {

        tree.Assignment = function (key, val) {
            this.key = key;
            this.value = val;
        };
        tree.Assignment.prototype = {
            type: "Assignment",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                if (this.value.eval) {
                    return new(tree.Assignment)(this.key, this.value.eval(env));
                }
                return this;
            },
            genCSS: function (env, output) {
                output.add(this.key + '=');
                if (this.value.genCSS) {
                    this.value.genCSS(env, output);
                } else {
                    output.add(this.value);
                }
            },
            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {

//
// A function call node.
//
        tree.Call = function (name, args, index, currentFileInfo) {
            this.name = name;
            this.args = args;
            this.index = index;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Call.prototype = {
            type: "Call",
            accept: function (visitor) {
                this.args = visitor.visit(this.args);
            },
            //
            // When evaluating a function call,
            // we either find the function in `tree.functions` [1],
            // in which case we call it, passing the  evaluated arguments,
            // if this returns null or we cannot find the function, we 
            // simply print it out as it appeared originally [2].
            //
            // The *functions.js* file contains the built-in functions.
            //
            // The reason why we evaluate the arguments, is in the case where
            // we try to pass a variable to a function, like: `saturate(@color)`.
            // The function should receive the value, not the variable.
            //
            eval: function (env) {
                var args = this.args.map(function (a) { return a.eval(env); }),
                    nameLC = this.name.toLowerCase(),
                    result, func;

                if (nameLC in tree.functions) { // 1.
                    try {
                        func = new tree.functionCall(env, this.currentFileInfo);
                        result = func[nameLC].apply(func, args);
                        /*jshint eqnull:true */
                        if (result != null) {
                            return result;
                        }
                    } catch (e) {
                        throw { type: e.type || "Runtime",
                            message: "error evaluating function `" + this.name + "`" +
                                (e.message ? ': ' + e.message : ''),
                            index: this.index, filename: this.currentFileInfo.filename };
                    }
                }

                return new tree.Call(this.name, args, this.index, this.currentFileInfo);
            },

            genCSS: function (env, output) {
                output.add(this.name + "(", this.currentFileInfo, this.index);

                for(var i = 0; i < this.args.length; i++) {
                    this.args[i].genCSS(env, output);
                    if (i + 1 < this.args.length) {
                        output.add(", ");
                    }
                }

                output.add(")");
            },

            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {
//
// RGB Colors - #ff0014, #eee
//
        tree.Color = function (rgb, a) {
            //
            // The end goal here, is to parse the arguments
            // into an integer triplet, such as `128, 255, 0`
            //
            // This facilitates operations and conversions.
            //
            if (Array.isArray(rgb)) {
                this.rgb = rgb;
            } else if (rgb.length == 6) {
                this.rgb = rgb.match(/.{2}/g).map(function (c) {
                    return parseInt(c, 16);
                });
            } else {
                this.rgb = rgb.split('').map(function (c) {
                    return parseInt(c + c, 16);
                });
            }
            this.alpha = typeof(a) === 'number' ? a : 1;
        };

        var transparentKeyword = "transparent";

        tree.Color.prototype = {
            type: "Color",
            eval: function () { return this; },
            luma: function () { return (0.2126 * this.rgb[0] / 255) + (0.7152 * this.rgb[1] / 255) + (0.0722 * this.rgb[2] / 255); },

            genCSS: function (env, output) {
                output.add(this.toCSS(env));
            },
            toCSS: function (env, doNotCompress) {
                var compress = env && env.compress && !doNotCompress;

                // If we have some transparency, the only way to represent it
                // is via `rgba`. Otherwise, we use the hex representation,
                // which has better compatibility with older browsers.
                // Values are capped between `0` and `255`, rounded and zero-padded.
                if (this.alpha < 1.0) {
                    if (this.alpha === 0 && this.isTransparentKeyword) {
                        return transparentKeyword;
                    }
                    return "rgba(" + this.rgb.map(function (c) {
                        return Math.round(c);
                    }).concat(this.alpha).join(',' + (compress ? '' : ' ')) + ")";
                } else {
                    var color = this.toRGB();

                    if (compress) {
                        var splitcolor = color.split('');

                        // Convert color to short format
                        if (splitcolor[1] === splitcolor[2] && splitcolor[3] === splitcolor[4] && splitcolor[5] === splitcolor[6]) {
                            color = '#' + splitcolor[1] + splitcolor[3] + splitcolor[5];
                        }
                    }

                    return color;
                }
            },

            //
            // Operations have to be done per-channel, if not,
            // channels will spill onto each other. Once we have
            // our result, in the form of an integer triplet,
            // we create a new Color node to hold the result.
            //
            operate: function (env, op, other) {
                var result = [];

                if (! (other instanceof tree.Color)) {
                    other = other.toColor();
                }

                for (var c = 0; c < 3; c++) {
                    result[c] = tree.operate(env, op, this.rgb[c], other.rgb[c]);
                }
                return new(tree.Color)(result, this.alpha + other.alpha);
            },

            toRGB: function () {
                return '#' + this.rgb.map(function (i) {
                    i = Math.round(i);
                    i = (i > 255 ? 255 : (i < 0 ? 0 : i)).toString(16);
                    return i.length === 1 ? '0' + i : i;
                }).join('');
            },

            toHSL: function () {
                var r = this.rgb[0] / 255,
                    g = this.rgb[1] / 255,
                    b = this.rgb[2] / 255,
                    a = this.alpha;

                var max = Math.max(r, g, b), min = Math.min(r, g, b);
                var h, s, l = (max + min) / 2, d = max - min;

                if (max === min) {
                    h = s = 0;
                } else {
                    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

                    switch (max) {
                        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                        case g: h = (b - r) / d + 2;               break;
                        case b: h = (r - g) / d + 4;               break;
                    }
                    h /= 6;
                }
                return { h: h * 360, s: s, l: l, a: a };
            },
            //Adapted from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
            toHSV: function () {
                var r = this.rgb[0] / 255,
                    g = this.rgb[1] / 255,
                    b = this.rgb[2] / 255,
                    a = this.alpha;

                var max = Math.max(r, g, b), min = Math.min(r, g, b);
                var h, s, v = max;

                var d = max - min;
                if (max === 0) {
                    s = 0;
                } else {
                    s = d / max;
                }

                if (max === min) {
                    h = 0;
                } else {
                    switch(max){
                        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                        case g: h = (b - r) / d + 2; break;
                        case b: h = (r - g) / d + 4; break;
                    }
                    h /= 6;
                }
                return { h: h * 360, s: s, v: v, a: a };
            },
            toARGB: function () {
                var argb = [Math.round(this.alpha * 255)].concat(this.rgb);
                return '#' + argb.map(function (i) {
                    i = Math.round(i);
                    i = (i > 255 ? 255 : (i < 0 ? 0 : i)).toString(16);
                    return i.length === 1 ? '0' + i : i;
                }).join('');
            },
            compare: function (x) {
                if (!x.rgb) {
                    return -1;
                }

                return (x.rgb[0] === this.rgb[0] &&
                    x.rgb[1] === this.rgb[1] &&
                    x.rgb[2] === this.rgb[2] &&
                    x.alpha === this.alpha) ? 0 : -1;
            }
        };

        tree.Color.fromKeyword = function(keyword) {
            if (tree.colors.hasOwnProperty(keyword)) {
                // detect named color
                return new(tree.Color)(tree.colors[keyword].slice(1));
            }
            if (keyword === transparentKeyword) {
                var transparent = new(tree.Color)([0, 0, 0], 0);
                transparent.isTransparentKeyword = true;
                return transparent;
            }
        };


    })(require('../tree'));

    (function (tree) {

        tree.Comment = function (value, silent, index, currentFileInfo) {
            this.value = value;
            this.silent = !!silent;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Comment.prototype = {
            type: "Comment",
            genCSS: function (env, output) {
                if (this.debugInfo) {
                    output.add(tree.debugInfo(env, this), this.currentFileInfo, this.index);
                }
                output.add(this.value.trim()); //TODO shouldn't need to trim, we shouldn't grab the \n
            },
            toCSS: tree.toCSS,
            isSilent: function(env) {
                var isReference = (this.currentFileInfo && this.currentFileInfo.reference && !this.isReferenced),
                    isCompressed = env.compress && !this.value.match(/^\/\*!/);
                return this.silent || isReference || isCompressed;
            },
            eval: function () { return this; },
            markReferenced: function () {
                this.isReferenced = true;
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Condition = function (op, l, r, i, negate) {
            this.op = op.trim();
            this.lvalue = l;
            this.rvalue = r;
            this.index = i;
            this.negate = negate;
        };
        tree.Condition.prototype = {
            type: "Condition",
            accept: function (visitor) {
                this.lvalue = visitor.visit(this.lvalue);
                this.rvalue = visitor.visit(this.rvalue);
            },
            eval: function (env) {
                var a = this.lvalue.eval(env),
                    b = this.rvalue.eval(env);

                var i = this.index, result;

                result = (function (op) {
                    switch (op) {
                        case 'and':
                            return a && b;
                        case 'or':
                            return a || b;
                        default:
                            if (a.compare) {
                                result = a.compare(b);
                            } else if (b.compare) {
                                result = b.compare(a);
                            } else {
                                throw { type: "Type",
                                    message: "Unable to perform comparison",
                                    index: i };
                            }
                            switch (result) {
                                case -1: return op === '<' || op === '=<' || op === '<=';
                                case  0: return op === '=' || op === '>=' || op === '=<' || op === '<=';
                                case  1: return op === '>' || op === '>=';
                            }
                    }
                })(this.op);
                return this.negate ? !result : result;
            }
        };

    })(require('../tree'));

    (function (tree) {

//
// A number with a unit
//
        tree.Dimension = function (value, unit) {
            this.value = parseFloat(value);
            this.unit = (unit && unit instanceof tree.Unit) ? unit :
                new(tree.Unit)(unit ? [unit] : undefined);
        };

        tree.Dimension.prototype = {
            type: "Dimension",
            accept: function (visitor) {
                this.unit = visitor.visit(this.unit);
            },
            eval: function (env) {
                return this;
            },
            toColor: function () {
                return new(tree.Color)([this.value, this.value, this.value]);
            },
            genCSS: function (env, output) {
                if ((env && env.strictUnits) && !this.unit.isSingular()) {
                    throw new Error("Multiple units in dimension. Correct the units or use the unit function. Bad unit: "+this.unit.toString());
                }

                var value = this.value,
                    strValue = String(value);

                if (value !== 0 && value < 0.000001 && value > -0.000001) {
                    // would be output 1e-6 etc.
                    strValue = value.toFixed(20).replace(/0+$/, "");
                }

                if (env && env.compress) {
                    // Zero values doesn't need a unit
                    if (value === 0 && this.unit.isLength()) {
                        output.add(strValue);
                        return;
                    }

                    // Float values doesn't need a leading zero
                    if (value > 0 && value < 1) {
                        strValue = (strValue).substr(1);
                    }
                }

                output.add(strValue);
                this.unit.genCSS(env, output);
            },
            toCSS: tree.toCSS,

            // In an operation between two Dimensions,
            // we default to the first Dimension's unit,
            // so `1px + 2` will yield `3px`.
            operate: function (env, op, other) {
                /*jshint noempty:false */
                var value = tree.operate(env, op, this.value, other.value),
                    unit = this.unit.clone();

                if (op === '+' || op === '-') {
                    if (unit.numerator.length === 0 && unit.denominator.length === 0) {
                        unit.numerator = other.unit.numerator.slice(0);
                        unit.denominator = other.unit.denominator.slice(0);
                    } else if (other.unit.numerator.length === 0 && unit.denominator.length === 0) {
                        // do nothing
                    } else {
                        other = other.convertTo(this.unit.usedUnits());

                        if(env.strictUnits && other.unit.toString() !== unit.toString()) {
                            throw new Error("Incompatible units. Change the units or use the unit function. Bad units: '" + unit.toString() +
                                "' and '" + other.unit.toString() + "'.");
                        }

                        value = tree.operate(env, op, this.value, other.value);
                    }
                } else if (op === '*') {
                    unit.numerator = unit.numerator.concat(other.unit.numerator).sort();
                    unit.denominator = unit.denominator.concat(other.unit.denominator).sort();
                    unit.cancel();
                } else if (op === '/') {
                    unit.numerator = unit.numerator.concat(other.unit.denominator).sort();
                    unit.denominator = unit.denominator.concat(other.unit.numerator).sort();
                    unit.cancel();
                }
                return new(tree.Dimension)(value, unit);
            },

            compare: function (other) {
                if (other instanceof tree.Dimension) {
                    var a = this.unify(), b = other.unify(),
                        aValue = a.value, bValue = b.value;

                    if (bValue > aValue) {
                        return -1;
                    } else if (bValue < aValue) {
                        return 1;
                    } else {
                        if (!b.unit.isEmpty() && a.unit.compare(b.unit) !== 0) {
                            return -1;
                        }
                        return 0;
                    }
                } else {
                    return -1;
                }
            },

            unify: function () {
                return this.convertTo({ length: 'm', duration: 's', angle: 'rad' });
            },

            convertTo: function (conversions) {
                var value = this.value, unit = this.unit.clone(),
                    i, groupName, group, targetUnit, derivedConversions = {}, applyUnit;

                if (typeof conversions === 'string') {
                    for(i in tree.UnitConversions) {
                        if (tree.UnitConversions[i].hasOwnProperty(conversions)) {
                            derivedConversions = {};
                            derivedConversions[i] = conversions;
                        }
                    }
                    conversions = derivedConversions;
                }
                applyUnit = function (atomicUnit, denominator) {
                    /*jshint loopfunc:true */
                    if (group.hasOwnProperty(atomicUnit)) {
                        if (denominator) {
                            value = value / (group[atomicUnit] / group[targetUnit]);
                        } else {
                            value = value * (group[atomicUnit] / group[targetUnit]);
                        }

                        return targetUnit;
                    }

                    return atomicUnit;
                };

                for (groupName in conversions) {
                    if (conversions.hasOwnProperty(groupName)) {
                        targetUnit = conversions[groupName];
                        group = tree.UnitConversions[groupName];

                        unit.map(applyUnit);
                    }
                }

                unit.cancel();

                return new(tree.Dimension)(value, unit);
            }
        };

// http://www.w3.org/TR/css3-values/#absolute-lengths
        tree.UnitConversions = {
            length: {
                'm': 1,
                'cm': 0.01,
                'mm': 0.001,
                'in': 0.0254,
                'pt': 0.0254 / 72,
                'pc': 0.0254 / 72 * 12
            },
            duration: {
                's': 1,
                'ms': 0.001
            },
            angle: {
                'rad': 1/(2*Math.PI),
                'deg': 1/360,
                'grad': 1/400,
                'turn': 1
            }
        };

        tree.Unit = function (numerator, denominator, backupUnit) {
            this.numerator = numerator ? numerator.slice(0).sort() : [];
            this.denominator = denominator ? denominator.slice(0).sort() : [];
            this.backupUnit = backupUnit;
        };

        tree.Unit.prototype = {
            type: "Unit",
            clone: function () {
                return new tree.Unit(this.numerator.slice(0), this.denominator.slice(0), this.backupUnit);
            },
            genCSS: function (env, output) {
                if (this.numerator.length >= 1) {
                    output.add(this.numerator[0]);
                } else
                if (this.denominator.length >= 1) {
                    output.add(this.denominator[0]);
                } else
                if ((!env || !env.strictUnits) && this.backupUnit) {
                    output.add(this.backupUnit);
                }
            },
            toCSS: tree.toCSS,

            toString: function () {
                var i, returnStr = this.numerator.join("*");
                for (i = 0; i < this.denominator.length; i++) {
                    returnStr += "/" + this.denominator[i];
                }
                return returnStr;
            },

            compare: function (other) {
                return this.is(other.toString()) ? 0 : -1;
            },

            is: function (unitString) {
                return this.toString() === unitString;
            },

            isLength: function () {
                return Boolean(this.toCSS().match(/px|em|%|in|cm|mm|pc|pt|ex/));
            },

            isEmpty: function () {
                return this.numerator.length === 0 && this.denominator.length === 0;
            },

            isSingular: function() {
                return this.numerator.length <= 1 && this.denominator.length === 0;
            },

            map: function(callback) {
                var i;

                for (i = 0; i < this.numerator.length; i++) {
                    this.numerator[i] = callback(this.numerator[i], false);
                }

                for (i = 0; i < this.denominator.length; i++) {
                    this.denominator[i] = callback(this.denominator[i], true);
                }
            },

            usedUnits: function() {
                var group, result = {}, mapUnit;

                mapUnit = function (atomicUnit) {
                    /*jshint loopfunc:true */
                    if (group.hasOwnProperty(atomicUnit) && !result[groupName]) {
                        result[groupName] = atomicUnit;
                    }

                    return atomicUnit;
                };

                for (var groupName in tree.UnitConversions) {
                    if (tree.UnitConversions.hasOwnProperty(groupName)) {
                        group = tree.UnitConversions[groupName];

                        this.map(mapUnit);
                    }
                }

                return result;
            },

            cancel: function () {
                var counter = {}, atomicUnit, i, backup;

                for (i = 0; i < this.numerator.length; i++) {
                    atomicUnit = this.numerator[i];
                    if (!backup) {
                        backup = atomicUnit;
                    }
                    counter[atomicUnit] = (counter[atomicUnit] || 0) + 1;
                }

                for (i = 0; i < this.denominator.length; i++) {
                    atomicUnit = this.denominator[i];
                    if (!backup) {
                        backup = atomicUnit;
                    }
                    counter[atomicUnit] = (counter[atomicUnit] || 0) - 1;
                }

                this.numerator = [];
                this.denominator = [];

                for (atomicUnit in counter) {
                    if (counter.hasOwnProperty(atomicUnit)) {
                        var count = counter[atomicUnit];

                        if (count > 0) {
                            for (i = 0; i < count; i++) {
                                this.numerator.push(atomicUnit);
                            }
                        } else if (count < 0) {
                            for (i = 0; i < -count; i++) {
                                this.denominator.push(atomicUnit);
                            }
                        }
                    }
                }

                if (this.numerator.length === 0 && this.denominator.length === 0 && backup) {
                    this.backupUnit = backup;
                }

                this.numerator.sort();
                this.denominator.sort();
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Directive = function (name, value, index, currentFileInfo) {
            this.name = name;

            if (Array.isArray(value)) {
                this.rules = [new(tree.Ruleset)([], value)];
                this.rules[0].allowImports = true;
            } else {
                this.value = value;
            }
            this.currentFileInfo = currentFileInfo;

        };
        tree.Directive.prototype = {
            type: "Directive",
            accept: function (visitor) {
                this.rules = visitor.visit(this.rules);
                this.value = visitor.visit(this.value);
            },
            genCSS: function (env, output) {
                output.add(this.name, this.currentFileInfo, this.index);
                if (this.rules) {
                    tree.outputRuleset(env, output, this.rules);
                } else {
                    output.add(' ');
                    this.value.genCSS(env, output);
                    output.add(';');
                }
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                var evaldDirective = this;
                if (this.rules) {
                    env.frames.unshift(this);
                    evaldDirective = new(tree.Directive)(this.name, null, this.index, this.currentFileInfo);
                    evaldDirective.rules = [this.rules[0].eval(env)];
                    evaldDirective.rules[0].root = true;
                    env.frames.shift();
                }
                return evaldDirective;
            },
            variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
            find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
            rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
            markReferenced: function () {
                var i, rules;
                this.isReferenced = true;
                if (this.rules) {
                    rules = this.rules[0].rules;
                    for (i = 0; i < rules.length; i++) {
                        if (rules[i].markReferenced) {
                            rules[i].markReferenced();
                        }
                    }
                }
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Element = function (combinator, value, index, currentFileInfo) {
            this.combinator = combinator instanceof tree.Combinator ?
                combinator : new(tree.Combinator)(combinator);

            if (typeof(value) === 'string') {
                this.value = value.trim();
            } else if (value) {
                this.value = value;
            } else {
                this.value = "";
            }
            this.index = index;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Element.prototype = {
            type: "Element",
            accept: function (visitor) {
                this.combinator = visitor.visit(this.combinator);
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                return new(tree.Element)(this.combinator,
                    this.value.eval ? this.value.eval(env) : this.value,
                    this.index,
                    this.currentFileInfo);
            },
            genCSS: function (env, output) {
                output.add(this.toCSS(env), this.currentFileInfo, this.index);
            },
            toCSS: function (env) {
                var value = (this.value.toCSS ? this.value.toCSS(env) : this.value);
                if (value === '' && this.combinator.value.charAt(0) === '&') {
                    return '';
                } else {
                    return this.combinator.toCSS(env || {}) + value;
                }
            }
        };

        tree.Attribute = function (key, op, value) {
            this.key = key;
            this.op = op;
            this.value = value;
        };
        tree.Attribute.prototype = {
            type: "Attribute",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                return new(tree.Attribute)(this.key.eval ? this.key.eval(env) : this.key,
                    this.op, (this.value && this.value.eval) ? this.value.eval(env) : this.value);
            },
            genCSS: function (env, output) {
                output.add(this.toCSS(env));
            },
            toCSS: function (env) {
                var value = this.key.toCSS ? this.key.toCSS(env) : this.key;

                if (this.op) {
                    value += this.op;
                    value += (this.value.toCSS ? this.value.toCSS(env) : this.value);
                }

                return '[' + value + ']';
            }
        };

        tree.Combinator = function (value) {
            if (value === ' ') {
                this.value = ' ';
            } else {
                this.value = value ? value.trim() : "";
            }
        };
        tree.Combinator.prototype = {
            type: "Combinator",
            _outputMap: {
                ''  : '',
                ' ' : ' ',
                ':' : ' :',
                '+' : ' + ',
                '~' : ' ~ ',
                '>' : ' > ',
                '|' : '|'
            },
            _outputMapCompressed: {
                ''  : '',
                ' ' : ' ',
                ':' : ' :',
                '+' : '+',
                '~' : '~',
                '>' : '>',
                '|' : '|'
            },
            genCSS: function (env, output) {
                output.add((env.compress ? this._outputMapCompressed : this._outputMap)[this.value]);
            },
            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {

        tree.Expression = function (value) { this.value = value; };
        tree.Expression.prototype = {
            type: "Expression",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                var returnValue,
                    inParenthesis = this.parens && !this.parensInOp,
                    doubleParen = false;
                if (inParenthesis) {
                    env.inParenthesis();
                }
                if (this.value.length > 1) {
                    returnValue = new(tree.Expression)(this.value.map(function (e) {
                        return e.eval(env);
                    }));
                } else if (this.value.length === 1) {
                    if (this.value[0].parens && !this.value[0].parensInOp) {
                        doubleParen = true;
                    }
                    returnValue = this.value[0].eval(env);
                } else {
                    returnValue = this;
                }
                if (inParenthesis) {
                    env.outOfParenthesis();
                }
                if (this.parens && this.parensInOp && !(env.isMathOn()) && !doubleParen) {
                    returnValue = new(tree.Paren)(returnValue);
                }
                return returnValue;
            },
            genCSS: function (env, output) {
                for(var i = 0; i < this.value.length; i++) {
                    this.value[i].genCSS(env, output);
                    if (i + 1 < this.value.length) {
                        output.add(" ");
                    }
                }
            },
            toCSS: tree.toCSS,
            throwAwayComments: function () {
                this.value = this.value.filter(function(v) {
                    return !(v instanceof tree.Comment);
                });
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Extend = function Extend(selector, option, index) {
            this.selector = selector;
            this.option = option;
            this.index = index;

            switch(option) {
                case "all":
                    this.allowBefore = true;
                    this.allowAfter = true;
                    break;
                default:
                    this.allowBefore = false;
                    this.allowAfter = false;
                    break;
            }
        };

        tree.Extend.prototype = {
            type: "Extend",
            accept: function (visitor) {
                this.selector = visitor.visit(this.selector);
            },
            eval: function (env) {
                return new(tree.Extend)(this.selector.eval(env), this.option, this.index);
            },
            clone: function (env) {
                return new(tree.Extend)(this.selector, this.option, this.index);
            },
            findSelfSelectors: function (selectors) {
                var selfElements = [],
                    i,
                    selectorElements;

                for(i = 0; i < selectors.length; i++) {
                    selectorElements = selectors[i].elements;
                    // duplicate the logic in genCSS function inside the selector node.
                    // future TODO - move both logics into the selector joiner visitor
                    if (i > 0 && selectorElements.length && selectorElements[0].combinator.value === "") {
                        selectorElements[0].combinator.value = ' ';
                    }
                    selfElements = selfElements.concat(selectors[i].elements);
                }

                this.selfSelectors = [{ elements: selfElements }];
            }
        };

    })(require('../tree'));

    (function (tree) {
//
// CSS @import node
//
// The general strategy here is that we don't want to wait
// for the parsing to be completed, before we start importing
// the file. That's because in the context of a browser,
// most of the time will be spent waiting for the server to respond.
//
// On creation, we push the import path to our import queue, though
// `import,push`, we also pass it a callback, which it'll call once
// the file has been fetched, and parsed.
//
        tree.Import = function (path, features, options, index, currentFileInfo) {
            this.options = options;
            this.index = index;
            this.path = path;
            this.features = features;
            this.currentFileInfo = currentFileInfo;

            if (this.options.less !== undefined || this.options.inline) {
                this.css = !this.options.less || this.options.inline;
            } else {
                var pathValue = this.getPath();
                if (pathValue && /css([\?;].*)?$/.test(pathValue)) {
                    this.css = true;
                }
            }
        };

//
// The actual import node doesn't return anything, when converted to CSS.
// The reason is that it's used at the evaluation stage, so that the rules
// it imports can be treated like any other rules.
//
// In `eval`, we make sure all Import nodes get evaluated, recursively, so
// we end up with a flat structure, which can easily be imported in the parent
// ruleset.
//
        tree.Import.prototype = {
            type: "Import",
            accept: function (visitor) {
                this.features = visitor.visit(this.features);
                this.path = visitor.visit(this.path);
                if (!this.options.inline) {
                    this.root = visitor.visit(this.root);
                }
            },
            genCSS: function (env, output) {
                if (this.css) {
                    output.add("@import ", this.currentFileInfo, this.index);
                    this.path.genCSS(env, output);
                    if (this.features) {
                        output.add(" ");
                        this.features.genCSS(env, output);
                    }
                    output.add(';');
                }
            },
            toCSS: tree.toCSS,
            getPath: function () {
                if (this.path instanceof tree.Quoted) {
                    var path = this.path.value;
                    return (this.css !== undefined || /(\.[a-z]*$)|([\?;].*)$/.test(path)) ? path : path + '.less';
                } else if (this.path instanceof tree.URL) {
                    return this.path.value.value;
                }
                return null;
            },
            evalForImport: function (env) {
                return new(tree.Import)(this.path.eval(env), this.features, this.options, this.index, this.currentFileInfo);
            },
            evalPath: function (env) {
                var path = this.path.eval(env);
                var rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;

                if (!(path instanceof tree.URL)) {
                    if (rootpath) {
                        var pathValue = path.value;
                        // Add the base path if the import is relative
                        if (pathValue && env.isPathRelative(pathValue)) {
                            path.value = rootpath + pathValue;
                        }
                    }
                    path.value = env.normalizePath(path.value);
                }

                return path;
            },
            eval: function (env) {
                var ruleset, features = this.features && this.features.eval(env);

                if (this.skip) { return []; }

                if (this.options.inline) {
                    //todo needs to reference css file not import
                    var contents = new(tree.Anonymous)(this.root, 0, {filename: this.importedFilename}, true);
                    return this.features ? new(tree.Media)([contents], this.features.value) : [contents];
                } else if (this.css) {
                    var newImport = new(tree.Import)(this.evalPath(env), features, this.options, this.index);
                    if (!newImport.css && this.error) {
                        throw this.error;
                    }
                    return newImport;
                } else {
                    ruleset = new(tree.Ruleset)([], this.root.rules.slice(0));

                    ruleset.evalImports(env);

                    return this.features ? new(tree.Media)(ruleset.rules, this.features.value) : ruleset.rules;
                }
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.JavaScript = function (string, index, escaped) {
            this.escaped = escaped;
            this.expression = string;
            this.index = index;
        };
        tree.JavaScript.prototype = {
            type: "JavaScript",
            eval: function (env) {
                var result,
                    that = this,
                    context = {};

                var expression = this.expression.replace(/@\{([\w-]+)\}/g, function (_, name) {
                    return tree.jsify(new(tree.Variable)('@' + name, that.index).eval(env));
                });

                try {
                    expression = new(Function)('return (' + expression + ')');
                } catch (e) {
                    throw { message: "JavaScript evaluation error: " + e.message + " from `" + expression + "`" ,
                        index: this.index };
                }

                for (var k in env.frames[0].variables()) {
                    /*jshint loopfunc:true */
                    context[k.slice(1)] = {
                        value: env.frames[0].variables()[k].value,
                        toJS: function () {
                            return this.value.eval(env).toCSS();
                        }
                    };
                }

                try {
                    result = expression.call(context);
                } catch (e) {
                    throw { message: "JavaScript evaluation error: '" + e.name + ': ' + e.message + "'" ,
                        index: this.index };
                }
                if (typeof(result) === 'string') {
                    return new(tree.Quoted)('"' + result + '"', result, this.escaped, this.index);
                } else if (Array.isArray(result)) {
                    return new(tree.Anonymous)(result.join(', '));
                } else {
                    return new(tree.Anonymous)(result);
                }
            }
        };

    })(require('../tree'));


    (function (tree) {

        tree.Keyword = function (value) { this.value = value; };
        tree.Keyword.prototype = {
            type: "Keyword",
            eval: function () { return this; },
            genCSS: function (env, output) {
                output.add(this.value);
            },
            toCSS: tree.toCSS,
            compare: function (other) {
                if (other instanceof tree.Keyword) {
                    return other.value === this.value ? 0 : 1;
                } else {
                    return -1;
                }
            }
        };

        tree.True = new(tree.Keyword)('true');
        tree.False = new(tree.Keyword)('false');

    })(require('../tree'));

    (function (tree) {

        tree.Media = function (value, features, index, currentFileInfo) {
            this.index = index;
            this.currentFileInfo = currentFileInfo;

            var selectors = this.emptySelectors();

            this.features = new(tree.Value)(features);
            this.rules = [new(tree.Ruleset)(selectors, value)];
            this.rules[0].allowImports = true;
        };
        tree.Media.prototype = {
            type: "Media",
            accept: function (visitor) {
                this.features = visitor.visit(this.features);
                this.rules = visitor.visit(this.rules);
            },
            genCSS: function (env, output) {
                output.add('@media ', this.currentFileInfo, this.index);
                this.features.genCSS(env, output);
                tree.outputRuleset(env, output, this.rules);
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                if (!env.mediaBlocks) {
                    env.mediaBlocks = [];
                    env.mediaPath = [];
                }

                var media = new(tree.Media)([], [], this.index, this.currentFileInfo);
                if(this.debugInfo) {
                    this.rules[0].debugInfo = this.debugInfo;
                    media.debugInfo = this.debugInfo;
                }
                var strictMathBypass = false;
                if (!env.strictMath) {
                    strictMathBypass = true;
                    env.strictMath = true;
                }
                try {
                    media.features = this.features.eval(env);
                }
                finally {
                    if (strictMathBypass) {
                        env.strictMath = false;
                    }
                }

                env.mediaPath.push(media);
                env.mediaBlocks.push(media);

                env.frames.unshift(this.rules[0]);
                media.rules = [this.rules[0].eval(env)];
                env.frames.shift();

                env.mediaPath.pop();

                return env.mediaPath.length === 0 ? media.evalTop(env) :
                    media.evalNested(env);
            },
            variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
            find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
            rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
            emptySelectors: function() {
                var el = new(tree.Element)('', '&', this.index, this.currentFileInfo);
                return [new(tree.Selector)([el], null, null, this.index, this.currentFileInfo)];
            },
            markReferenced: function () {
                var i, rules = this.rules[0].rules;
                this.isReferenced = true;
                for (i = 0; i < rules.length; i++) {
                    if (rules[i].markReferenced) {
                        rules[i].markReferenced();
                    }
                }
            },

            evalTop: function (env) {
                var result = this;

                // Render all dependent Media blocks.
                if (env.mediaBlocks.length > 1) {
                    var selectors = this.emptySelectors();
                    result = new(tree.Ruleset)(selectors, env.mediaBlocks);
                    result.multiMedia = true;
                }

                delete env.mediaBlocks;
                delete env.mediaPath;

                return result;
            },
            evalNested: function (env) {
                var i, value,
                    path = env.mediaPath.concat([this]);

                // Extract the media-query conditions separated with `,` (OR).
                for (i = 0; i < path.length; i++) {
                    value = path[i].features instanceof tree.Value ?
                        path[i].features.value : path[i].features;
                    path[i] = Array.isArray(value) ? value : [value];
                }

                // Trace all permutations to generate the resulting media-query.
                //
                // (a, b and c) with nested (d, e) ->
                //    a and d
                //    a and e
                //    b and c and d
                //    b and c and e
                this.features = new(tree.Value)(this.permute(path).map(function (path) {
                    path = path.map(function (fragment) {
                        return fragment.toCSS ? fragment : new(tree.Anonymous)(fragment);
                    });

                    for(i = path.length - 1; i > 0; i--) {
                        path.splice(i, 0, new(tree.Anonymous)("and"));
                    }

                    return new(tree.Expression)(path);
                }));

                // Fake a tree-node that doesn't output anything.
                return new(tree.Ruleset)([], []);
            },
            permute: function (arr) {
                if (arr.length === 0) {
                    return [];
                } else if (arr.length === 1) {
                    return arr[0];
                } else {
                    var result = [];
                    var rest = this.permute(arr.slice(1));
                    for (var i = 0; i < rest.length; i++) {
                        for (var j = 0; j < arr[0].length; j++) {
                            result.push([arr[0][j]].concat(rest[i]));
                        }
                    }
                    return result;
                }
            },
            bubbleSelectors: function (selectors) {
                this.rules = [new(tree.Ruleset)(selectors.slice(0), [this.rules[0]])];
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.mixin = {};
        tree.mixin.Call = function (elements, args, index, currentFileInfo, important) {
            this.selector = new(tree.Selector)(elements);
            this.arguments = args;
            this.index = index;
            this.currentFileInfo = currentFileInfo;
            this.important = important;
        };
        tree.mixin.Call.prototype = {
            type: "MixinCall",
            accept: function (visitor) {
                this.selector = visitor.visit(this.selector);
                this.arguments = visitor.visit(this.arguments);
            },
            eval: function (env) {
                var mixins, mixin, args, rules = [], match = false, i, m, f, isRecursive, isOneFound, rule;

                args = this.arguments && this.arguments.map(function (a) {
                    return { name: a.name, value: a.value.eval(env) };
                });

                for (i = 0; i < env.frames.length; i++) {
                    if ((mixins = env.frames[i].find(this.selector)).length > 0) {
                        isOneFound = true;
                        for (m = 0; m < mixins.length; m++) {
                            mixin = mixins[m];
                            isRecursive = false;
                            for(f = 0; f < env.frames.length; f++) {
                                if ((!(mixin instanceof tree.mixin.Definition)) && mixin === (env.frames[f].originalRuleset || env.frames[f])) {
                                    isRecursive = true;
                                    break;
                                }
                            }
                            if (isRecursive) {
                                continue;
                            }
                            if (mixin.matchArgs(args, env)) {
                                if (!mixin.matchCondition || mixin.matchCondition(args, env)) {
                                    try {
                                        if (!(mixin instanceof tree.mixin.Definition)) {
                                            mixin = new tree.mixin.Definition("", [], mixin.rules, null, false);
                                            mixin.originalRuleset = mixins[m].originalRuleset || mixins[m];
                                        }
                                        //if (this.important) {
                                        //    isImportant = env.isImportant;
                                        //    env.isImportant = true;
                                        //}
                                        Array.prototype.push.apply(
                                            rules, mixin.eval(env, args, this.important).rules);
                                        //if (this.important) {
                                        //    env.isImportant = isImportant;
                                        //}
                                    } catch (e) {
                                        throw { message: e.message, index: this.index, filename: this.currentFileInfo.filename, stack: e.stack };
                                    }
                                }
                                match = true;
                            }
                        }
                        if (match) {
                            if (!this.currentFileInfo || !this.currentFileInfo.reference) {
                                for (i = 0; i < rules.length; i++) {
                                    rule = rules[i];
                                    if (rule.markReferenced) {
                                        rule.markReferenced();
                                    }
                                }
                            }
                            return rules;
                        }
                    }
                }
                if (isOneFound) {
                    throw { type:    'Runtime',
                        message: 'No matching definition was found for `' +
                            this.selector.toCSS().trim() + '('      +
                            (args ? args.map(function (a) {
                                var argValue = "";
                                if (a.name) {
                                    argValue += a.name + ":";
                                }
                                if (a.value.toCSS) {
                                    argValue += a.value.toCSS();
                                } else {
                                    argValue += "???";
                                }
                                return argValue;
                            }).join(', ') : "") + ")`",
                        index:   this.index, filename: this.currentFileInfo.filename };
                } else {
                    throw { type: 'Name',
                        message: this.selector.toCSS().trim() + " is undefined",
                        index: this.index, filename: this.currentFileInfo.filename };
                }
            }
        };

        tree.mixin.Definition = function (name, params, rules, condition, variadic) {
            this.name = name;
            this.selectors = [new(tree.Selector)([new(tree.Element)(null, name, this.index, this.currentFileInfo)])];
            this.params = params;
            this.condition = condition;
            this.variadic = variadic;
            this.arity = params.length;
            this.rules = rules;
            this._lookups = {};
            this.required = params.reduce(function (count, p) {
                if (!p.name || (p.name && !p.value)) { return count + 1; }
                else                                 { return count; }
            }, 0);
            this.parent = tree.Ruleset.prototype;
            this.frames = [];
        };
        tree.mixin.Definition.prototype = {
            type: "MixinDefinition",
            accept: function (visitor) {
                this.params = visitor.visit(this.params);
                this.rules = visitor.visit(this.rules);
                this.condition = visitor.visit(this.condition);
            },
            variable:  function (name) { return this.parent.variable.call(this, name); },
            variables: function ()     { return this.parent.variables.call(this); },
            find:      function ()     { return this.parent.find.apply(this, arguments); },
            rulesets:  function ()     { return this.parent.rulesets.apply(this); },

            evalParams: function (env, mixinEnv, args, evaldArguments) {
                /*jshint boss:true */
                var frame = new(tree.Ruleset)(null, []),
                    varargs, arg,
                    params = this.params.slice(0),
                    i, j, val, name, isNamedFound, argIndex;

                mixinEnv = new tree.evalEnv(mixinEnv, [frame].concat(mixinEnv.frames));

                if (args) {
                    args = args.slice(0);

                    for(i = 0; i < args.length; i++) {
                        arg = args[i];
                        if (name = (arg && arg.name)) {
                            isNamedFound = false;
                            for(j = 0; j < params.length; j++) {
                                if (!evaldArguments[j] && name === params[j].name) {
                                    evaldArguments[j] = arg.value.eval(env);
                                    frame.rules.unshift(new(tree.Rule)(name, arg.value.eval(env)));
                                    isNamedFound = true;
                                    break;
                                }
                            }
                            if (isNamedFound) {
                                args.splice(i, 1);
                                i--;
                                continue;
                            } else {
                                throw { type: 'Runtime', message: "Named argument for " + this.name +
                                    ' ' + args[i].name + ' not found' };
                            }
                        }
                    }
                }
                argIndex = 0;
                for (i = 0; i < params.length; i++) {
                    if (evaldArguments[i]) { continue; }

                    arg = args && args[argIndex];

                    if (name = params[i].name) {
                        if (params[i].variadic && args) {
                            varargs = [];
                            for (j = argIndex; j < args.length; j++) {
                                varargs.push(args[j].value.eval(env));
                            }
                            frame.rules.unshift(new(tree.Rule)(name, new(tree.Expression)(varargs).eval(env)));
                        } else {
                            val = arg && arg.value;
                            if (val) {
                                val = val.eval(env);
                            } else if (params[i].value) {
                                val = params[i].value.eval(mixinEnv);
                                frame.resetCache();
                            } else {
                                throw { type: 'Runtime', message: "wrong number of arguments for " + this.name +
                                    ' (' + args.length + ' for ' + this.arity + ')' };
                            }

                            frame.rules.unshift(new(tree.Rule)(name, val));
                            evaldArguments[i] = val;
                        }
                    }

                    if (params[i].variadic && args) {
                        for (j = argIndex; j < args.length; j++) {
                            evaldArguments[j] = args[j].value.eval(env);
                        }
                    }
                    argIndex++;
                }

                return frame;
            },
            eval: function (env, args, important) {
                var _arguments = [],
                    mixinFrames = this.frames.concat(env.frames),
                    frame = this.evalParams(env, new(tree.evalEnv)(env, mixinFrames), args, _arguments),
                    rules, ruleset;

                frame.rules.unshift(new(tree.Rule)('@arguments', new(tree.Expression)(_arguments).eval(env)));

                rules = this.rules.slice(0);

                ruleset = new(tree.Ruleset)(null, rules);
                ruleset.originalRuleset = this;
                ruleset = ruleset.eval(new(tree.evalEnv)(env, [this, frame].concat(mixinFrames)));
                if (important) {
                    ruleset = this.parent.makeImportant.apply(ruleset);
                }
                return ruleset;
            },
            matchCondition: function (args, env) {
                if (this.condition && !this.condition.eval(
                    new(tree.evalEnv)(env,
                        [this.evalParams(env, new(tree.evalEnv)(env, this.frames.concat(env.frames)), args, [])] // the parameter variables
                            .concat(this.frames) // the parent namespace/mixin frames
                            .concat(env.frames)))) { // the current environment frames
                    return false;
                }
                return true;
            },
            matchArgs: function (args, env) {
                var argsLength = (args && args.length) || 0, len;

                if (! this.variadic) {
                    if (argsLength < this.required)                               { return false; }
                    if (argsLength > this.params.length)                          { return false; }
                } else {
                    if (argsLength < (this.required - 1))                         { return false; }
                }

                len = Math.min(argsLength, this.arity);

                for (var i = 0; i < len; i++) {
                    if (!this.params[i].name && !this.params[i].variadic) {
                        if (args[i].value.eval(env).toCSS() != this.params[i].value.eval(env).toCSS()) {
                            return false;
                        }
                    }
                }
                return true;
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Negative = function (node) {
            this.value = node;
        };
        tree.Negative.prototype = {
            type: "Negative",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            genCSS: function (env, output) {
                output.add('-');
                this.value.genCSS(env, output);
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                if (env.isMathOn()) {
                    return (new(tree.Operation)('*', [new(tree.Dimension)(-1), this.value])).eval(env);
                }
                return new(tree.Negative)(this.value.eval(env));
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Operation = function (op, operands, isSpaced) {
            this.op = op.trim();
            this.operands = operands;
            this.isSpaced = isSpaced;
        };
        tree.Operation.prototype = {
            type: "Operation",
            accept: function (visitor) {
                this.operands = visitor.visit(this.operands);
            },
            eval: function (env) {
                var a = this.operands[0].eval(env),
                    b = this.operands[1].eval(env),
                    temp;

                if (env.isMathOn()) {
                    if (a instanceof tree.Dimension && b instanceof tree.Color) {
                        if (this.op === '*' || this.op === '+') {
                            temp = b, b = a, a = temp;
                        } else {
                            throw { type: "Operation",
                                message: "Can't substract or divide a color from a number" };
                        }
                    }
                    if (!a.operate) {
                        throw { type: "Operation",
                            message: "Operation on an invalid type" };
                    }

                    return a.operate(env, this.op, b);
                } else {
                    return new(tree.Operation)(this.op, [a, b], this.isSpaced);
                }
            },
            genCSS: function (env, output) {
                this.operands[0].genCSS(env, output);
                if (this.isSpaced) {
                    output.add(" ");
                }
                output.add(this.op);
                if (this.isSpaced) {
                    output.add(" ");
                }
                this.operands[1].genCSS(env, output);
            },
            toCSS: tree.toCSS
        };

        tree.operate = function (env, op, a, b) {
            switch (op) {
                case '+': return a + b;
                case '-': return a - b;
                case '*': return a * b;
                case '/': return a / b;
            }
        };

    })(require('../tree'));


    (function (tree) {

        tree.Paren = function (node) {
            this.value = node;
        };
        tree.Paren.prototype = {
            type: "Paren",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            genCSS: function (env, output) {
                output.add('(');
                this.value.genCSS(env, output);
                output.add(')');
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                return new(tree.Paren)(this.value.eval(env));
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Quoted = function (str, content, escaped, index, currentFileInfo) {
            this.escaped = escaped;
            this.value = content || '';
            this.quote = str.charAt(0);
            this.index = index;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Quoted.prototype = {
            type: "Quoted",
            genCSS: function (env, output) {
                if (!this.escaped) {
                    output.add(this.quote, this.currentFileInfo, this.index);
                }
                output.add(this.value);
                if (!this.escaped) {
                    output.add(this.quote);
                }
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                var that = this;
                var value = this.value.replace(/`([^`]+)`/g, function (_, exp) {
                    return new(tree.JavaScript)(exp, that.index, true).eval(env).value;
                }).replace(/@\{([\w-]+)\}/g, function (_, name) {
                        var v = new(tree.Variable)('@' + name, that.index, that.currentFileInfo).eval(env, true);
                        return (v instanceof tree.Quoted) ? v.value : v.toCSS();
                    });
                return new(tree.Quoted)(this.quote + value + this.quote, value, this.escaped, this.index, this.currentFileInfo);
            },
            compare: function (x) {
                if (!x.toCSS) {
                    return -1;
                }

                var left = this.toCSS(),
                    right = x.toCSS();

                if (left === right) {
                    return 0;
                }

                return left < right ? -1 : 1;
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline) {
            this.name = name;
            this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
            this.important = important ? ' ' + important.trim() : '';
            this.merge = merge;
            this.index = index;
            this.currentFileInfo = currentFileInfo;
            this.inline = inline || false;
            this.variable = (name.charAt(0) === '@');
        };

        tree.Rule.prototype = {
            type: "Rule",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            genCSS: function (env, output) {
                output.add(this.name + (env.compress ? ':' : ': '), this.currentFileInfo, this.index);
                try {
                    this.value.genCSS(env, output);
                }
                catch(e) {
                    e.index = this.index;
                    e.filename = this.currentFileInfo.filename;
                    throw e;
                }
                output.add(this.important + ((this.inline || (env.lastRule && env.compress)) ? "" : ";"), this.currentFileInfo, this.index);
            },
            toCSS: tree.toCSS,
            eval: function (env) {
                var strictMathBypass = false;
                if (this.name === "font" && !env.strictMath) {
                    strictMathBypass = true;
                    env.strictMath = true;
                }
                try {
                    return new(tree.Rule)(this.name,
                        this.value.eval(env),
                        this.important,
                        this.merge,
                        this.index, this.currentFileInfo, this.inline);
                }
                finally {
                    if (strictMathBypass) {
                        env.strictMath = false;
                    }
                }
            },
            makeImportant: function () {
                return new(tree.Rule)(this.name,
                    this.value,
                    "!important",
                    this.merge,
                    this.index, this.currentFileInfo, this.inline);
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Ruleset = function (selectors, rules, strictImports) {
            this.selectors = selectors;
            this.rules = rules;
            this._lookups = {};
            this.strictImports = strictImports;
        };
        tree.Ruleset.prototype = {
            type: "Ruleset",
            accept: function (visitor) {
                if (this.paths) {
                    for(var i = 0; i < this.paths.length; i++) {
                        this.paths[i] = visitor.visit(this.paths[i]);
                    }
                } else {
                    this.selectors = visitor.visit(this.selectors);
                }
                this.rules = visitor.visit(this.rules);
            },
            eval: function (env) {
                var selectors = this.selectors && this.selectors.map(function (s) { return s.eval(env); });
                var ruleset = new(tree.Ruleset)(selectors, this.rules.slice(0), this.strictImports);
                var rules;
                var rule;
                var i;

                ruleset.originalRuleset = this;
                ruleset.root = this.root;
                ruleset.firstRoot = this.firstRoot;
                ruleset.allowImports = this.allowImports;

                if(this.debugInfo) {
                    ruleset.debugInfo = this.debugInfo;
                }

                // push the current ruleset to the frames stack
                env.frames.unshift(ruleset);

                // currrent selectors
                if (!env.selectors) {
                    env.selectors = [];
                }
                env.selectors.unshift(this.selectors);

                // Evaluate imports
                if (ruleset.root || ruleset.allowImports || !ruleset.strictImports) {
                    ruleset.evalImports(env);
                }

                // Store the frames around mixin definitions,
                // so they can be evaluated like closures when the time comes.
                for (i = 0; i < ruleset.rules.length; i++) {
                    if (ruleset.rules[i] instanceof tree.mixin.Definition) {
                        ruleset.rules[i].frames = env.frames.slice(0);
                    }
                }

                var mediaBlockCount = (env.mediaBlocks && env.mediaBlocks.length) || 0;

                // Evaluate mixin calls.
                for (i = 0; i < ruleset.rules.length; i++) {
                    if (ruleset.rules[i] instanceof tree.mixin.Call) {
                        /*jshint loopfunc:true */
                        rules = ruleset.rules[i].eval(env).filter(function(r) {
                            if ((r instanceof tree.Rule) && r.variable) {
                                // do not pollute the scope if the variable is
                                // already there. consider returning false here
                                // but we need a way to "return" variable from mixins
                                return !(ruleset.variable(r.name));
                            }
                            return true;
                        });
                        ruleset.rules.splice.apply(ruleset.rules, [i, 1].concat(rules));
                        i += rules.length-1;
                        ruleset.resetCache();
                    }
                }

                // Evaluate everything else
                for (i = 0; i < ruleset.rules.length; i++) {
                    rule = ruleset.rules[i];

                    if (! (rule instanceof tree.mixin.Definition)) {
                        ruleset.rules[i] = rule.eval ? rule.eval(env) : rule;
                    }
                }

                // Pop the stack
                env.frames.shift();
                env.selectors.shift();

                if (env.mediaBlocks) {
                    for (i = mediaBlockCount; i < env.mediaBlocks.length; i++) {
                        env.mediaBlocks[i].bubbleSelectors(selectors);
                    }
                }

                return ruleset;
            },
            evalImports: function(env) {
                var i, rules;
                for (i = 0; i < this.rules.length; i++) {
                    if (this.rules[i] instanceof tree.Import) {
                        rules = this.rules[i].eval(env);
                        if (typeof rules.length === "number") {
                            this.rules.splice.apply(this.rules, [i, 1].concat(rules));
                            i+= rules.length-1;
                        } else {
                            this.rules.splice(i, 1, rules);
                        }
                        this.resetCache();
                    }
                }
            },
            makeImportant: function() {
                return new tree.Ruleset(this.selectors, this.rules.map(function (r) {
                    if (r.makeImportant) {
                        return r.makeImportant();
                    } else {
                        return r;
                    }
                }), this.strictImports);
            },
            matchArgs: function (args) {
                return !args || args.length === 0;
            },
            matchCondition: function (args, env) {
                var lastSelector = this.selectors[this.selectors.length-1];
                if (lastSelector.condition &&
                    !lastSelector.condition.eval(
                        new(tree.evalEnv)(env,
                            env.frames))) {
                    return false;
                }
                return true;
            },
            resetCache: function () {
                this._rulesets = null;
                this._variables = null;
                this._lookups = {};
            },
            variables: function () {
                if (this._variables) { return this._variables; }
                else {
                    return this._variables = this.rules.reduce(function (hash, r) {
                        if (r instanceof tree.Rule && r.variable === true) {
                            hash[r.name] = r;
                        }
                        return hash;
                    }, {});
                }
            },
            variable: function (name) {
                return this.variables()[name];
            },
            rulesets: function () {
                return this.rules.filter(function (r) {
                    return (r instanceof tree.Ruleset) || (r instanceof tree.mixin.Definition);
                });
            },
            find: function (selector, self) {
                self = self || this;
                var rules = [], match,
                    key = selector.toCSS();

                if (key in this._lookups) { return this._lookups[key]; }

                this.rulesets().forEach(function (rule) {
                    if (rule !== self) {
                        for (var j = 0; j < rule.selectors.length; j++) {
                            if (match = selector.match(rule.selectors[j])) {
                                if (selector.elements.length > rule.selectors[j].elements.length) {
                                    Array.prototype.push.apply(rules, rule.find(
                                        new(tree.Selector)(selector.elements.slice(1)), self));
                                } else {
                                    rules.push(rule);
                                }
                                break;
                            }
                        }
                    }
                });
                return this._lookups[key] = rules;
            },
            genCSS: function (env, output) {
                var i, j,
                    ruleNodes = [],
                    rulesetNodes = [],
                    debugInfo,     // Line number debugging
                    rule,
                    firstRuleset = true,
                    path;

                env.tabLevel = (env.tabLevel || 0);

                if (!this.root) {
                    env.tabLevel++;
                }

                var tabRuleStr = env.compress ? '' : Array(env.tabLevel + 1).join("  "),
                    tabSetStr = env.compress ? '' : Array(env.tabLevel).join("  ");

                for (i = 0; i < this.rules.length; i++) {
                    rule = this.rules[i];
                    if (rule.rules || (rule instanceof tree.Media) || rule instanceof tree.Directive || (this.root && rule instanceof tree.Comment)) {
                        rulesetNodes.push(rule);
                    } else {
                        ruleNodes.push(rule);
                    }
                }

                // If this is the root node, we don't render
                // a selector, or {}.
                if (!this.root) {
                    debugInfo = tree.debugInfo(env, this, tabSetStr);

                    if (debugInfo) {
                        output.add(debugInfo);
                        output.add(tabSetStr);
                    }

                    for(i = 0; i < this.paths.length; i++) {
                        path = this.paths[i];
                        env.firstSelector = true;
                        for(j = 0; j < path.length; j++) {
                            path[j].genCSS(env, output);
                            env.firstSelector = false;
                        }
                        if (i + 1 < this.paths.length) {
                            output.add(env.compress ? ',' : (',\n' + tabSetStr));
                        }
                    }

                    output.add((env.compress ? '{' : ' {\n') + tabRuleStr);
                }

                // Compile rules and rulesets
                for (i = 0; i < ruleNodes.length; i++) {
                    rule = ruleNodes[i];

                    // @page{ directive ends up with root elements inside it, a mix of rules and rulesets
                    // In this instance we do not know whether it is the last property
                    if (i + 1 === ruleNodes.length && (!this.root || rulesetNodes.length === 0 || this.firstRoot)) {
                        env.lastRule = true;
                    }

                    if (rule.genCSS) {
                        rule.genCSS(env, output);
                    } else if (rule.value) {
                        output.add(rule.value.toString());
                    }

                    if (!env.lastRule) {
                        output.add(env.compress ? '' : ('\n' + tabRuleStr));
                    } else {
                        env.lastRule = false;
                    }
                }

                if (!this.root) {
                    output.add((env.compress ? '}' : '\n' + tabSetStr + '}'));
                    env.tabLevel--;
                }

                for (i = 0; i < rulesetNodes.length; i++) {
                    if (ruleNodes.length && firstRuleset) {
                        output.add((env.compress ? "" : "\n") + (this.root ? tabRuleStr : tabSetStr));
                    }
                    if (!firstRuleset) {
                        output.add((env.compress ? "" : "\n") + (this.root ? tabRuleStr : tabSetStr));
                    }
                    firstRuleset = false;
                    rulesetNodes[i].genCSS(env, output);
                }

                if (!output.isEmpty() && !env.compress && this.firstRoot) {
                    output.add('\n');
                }
            },

            toCSS: tree.toCSS,

            markReferenced: function () {
                for (var s = 0; s < this.selectors.length; s++) {
                    this.selectors[s].markReferenced();
                }
            },

            joinSelectors: function (paths, context, selectors) {
                for (var s = 0; s < selectors.length; s++) {
                    this.joinSelector(paths, context, selectors[s]);
                }
            },

            joinSelector: function (paths, context, selector) {

                var i, j, k,
                    hasParentSelector, newSelectors, el, sel, parentSel,
                    newSelectorPath, afterParentJoin, newJoinedSelector,
                    newJoinedSelectorEmpty, lastSelector, currentElements,
                    selectorsMultiplied;

                for (i = 0; i < selector.elements.length; i++) {
                    el = selector.elements[i];
                    if (el.value === '&') {
                        hasParentSelector = true;
                    }
                }

                if (!hasParentSelector) {
                    if (context.length > 0) {
                        for (i = 0; i < context.length; i++) {
                            paths.push(context[i].concat(selector));
                        }
                    }
                    else {
                        paths.push([selector]);
                    }
                    return;
                }

                // The paths are [[Selector]]
                // The first list is a list of comma seperated selectors
                // The inner list is a list of inheritance seperated selectors
                // e.g.
                // .a, .b {
                //   .c {
                //   }
                // }
                // == [[.a] [.c]] [[.b] [.c]]
                //

                // the elements from the current selector so far
                currentElements = [];
                // the current list of new selectors to add to the path.
                // We will build it up. We initiate it with one empty selector as we "multiply" the new selectors
                // by the parents
                newSelectors = [[]];

                for (i = 0; i < selector.elements.length; i++) {
                    el = selector.elements[i];
                    // non parent reference elements just get added
                    if (el.value !== "&") {
                        currentElements.push(el);
                    } else {
                        // the new list of selectors to add
                        selectorsMultiplied = [];

                        // merge the current list of non parent selector elements
                        // on to the current list of selectors to add
                        if (currentElements.length > 0) {
                            this.mergeElementsOnToSelectors(currentElements, newSelectors);
                        }

                        // loop through our current selectors
                        for (j = 0; j < newSelectors.length; j++) {
                            sel = newSelectors[j];
                            // if we don't have any parent paths, the & might be in a mixin so that it can be used
                            // whether there are parents or not
                            if (context.length === 0) {
                                // the combinator used on el should now be applied to the next element instead so that
                                // it is not lost
                                if (sel.length > 0) {
                                    sel[0].elements = sel[0].elements.slice(0);
                                    sel[0].elements.push(new(tree.Element)(el.combinator, '', 0, el.index, el.currentFileInfo));
                                }
                                selectorsMultiplied.push(sel);
                            }
                            else {
                                // and the parent selectors
                                for (k = 0; k < context.length; k++) {
                                    parentSel = context[k];
                                    // We need to put the current selectors
                                    // then join the last selector's elements on to the parents selectors

                                    // our new selector path
                                    newSelectorPath = [];
                                    // selectors from the parent after the join
                                    afterParentJoin = [];
                                    newJoinedSelectorEmpty = true;

                                    //construct the joined selector - if & is the first thing this will be empty,
                                    // if not newJoinedSelector will be the last set of elements in the selector
                                    if (sel.length > 0) {
                                        newSelectorPath = sel.slice(0);
                                        lastSelector = newSelectorPath.pop();
                                        newJoinedSelector = selector.createDerived(lastSelector.elements.slice(0));
                                        newJoinedSelectorEmpty = false;
                                    }
                                    else {
                                        newJoinedSelector = selector.createDerived([]);
                                    }

                                    //put together the parent selectors after the join
                                    if (parentSel.length > 1) {
                                        afterParentJoin = afterParentJoin.concat(parentSel.slice(1));
                                    }

                                    if (parentSel.length > 0) {
                                        newJoinedSelectorEmpty = false;

                                        // join the elements so far with the first part of the parent
                                        newJoinedSelector.elements.push(new(tree.Element)(el.combinator, parentSel[0].elements[0].value, el.index, el.currentFileInfo));
                                        newJoinedSelector.elements = newJoinedSelector.elements.concat(parentSel[0].elements.slice(1));
                                    }

                                    if (!newJoinedSelectorEmpty) {
                                        // now add the joined selector
                                        newSelectorPath.push(newJoinedSelector);
                                    }

                                    // and the rest of the parent
                                    newSelectorPath = newSelectorPath.concat(afterParentJoin);

                                    // add that to our new set of selectors
                                    selectorsMultiplied.push(newSelectorPath);
                                }
                            }
                        }

                        // our new selectors has been multiplied, so reset the state
                        newSelectors = selectorsMultiplied;
                        currentElements = [];
                    }
                }

                // if we have any elements left over (e.g. .a& .b == .b)
                // add them on to all the current selectors
                if (currentElements.length > 0) {
                    this.mergeElementsOnToSelectors(currentElements, newSelectors);
                }

                for (i = 0; i < newSelectors.length; i++) {
                    if (newSelectors[i].length > 0) {
                        paths.push(newSelectors[i]);
                    }
                }
            },

            mergeElementsOnToSelectors: function(elements, selectors) {
                var i, sel;

                if (selectors.length === 0) {
                    selectors.push([ new(tree.Selector)(elements) ]);
                    return;
                }

                for (i = 0; i < selectors.length; i++) {
                    sel = selectors[i];

                    // if the previous thing in sel is a parent this needs to join on to it
                    if (sel.length > 0) {
                        sel[sel.length - 1] = sel[sel.length - 1].createDerived(sel[sel.length - 1].elements.concat(elements));
                    }
                    else {
                        sel.push(new(tree.Selector)(elements));
                    }
                }
            }
        };
    })(require('../tree'));

    (function (tree) {

        tree.Selector = function (elements, extendList, condition, index, currentFileInfo, isReferenced) {
            this.elements = elements;
            this.extendList = extendList || [];
            this.condition = condition;
            this.currentFileInfo = currentFileInfo || {};
            this.isReferenced = isReferenced;
            if (!condition) {
                this.evaldCondition = true;
            }
        };
        tree.Selector.prototype = {
            type: "Selector",
            accept: function (visitor) {
                this.elements = visitor.visit(this.elements);
                this.extendList = visitor.visit(this.extendList);
                this.condition = visitor.visit(this.condition);
            },
            createDerived: function(elements, extendList, evaldCondition) {
                /*jshint eqnull:true */
                evaldCondition = evaldCondition != null ? evaldCondition : this.evaldCondition;
                var newSelector = new(tree.Selector)(elements, extendList || this.extendList, this.condition, this.index, this.currentFileInfo, this.isReferenced);
                newSelector.evaldCondition = evaldCondition;
                return newSelector;
            },
            match: function (other) {
                var elements = this.elements,
                    len = elements.length,
                    oelements, olen, max, i;

                oelements = other.elements.slice(
                    (other.elements.length && other.elements[0].value === "&") ? 1 : 0);
                olen = oelements.length;
                max = Math.min(len, olen);

                if (olen === 0 || len < olen) {
                    return false;
                } else {
                    for (i = 0; i < max; i++) {
                        if (elements[i].value !== oelements[i].value) {
                            return false;
                        }
                    }
                }
                return true;
            },
            eval: function (env) {
                var evaldCondition = this.condition && this.condition.eval(env);

                return this.createDerived(this.elements.map(function (e) {
                    return e.eval(env);
                }), this.extendList.map(function(extend) {
                    return extend.eval(env);
                }), evaldCondition);
            },
            genCSS: function (env, output) {
                var i, element;
                if ((!env || !env.firstSelector) && this.elements[0].combinator.value === "") {
                    output.add(' ', this.currentFileInfo, this.index);
                }
                if (!this._css) {
                    //TODO caching? speed comparison?
                    for(i = 0; i < this.elements.length; i++) {
                        element = this.elements[i];
                        element.genCSS(env, output);
                    }
                }
            },
            toCSS: tree.toCSS,
            markReferenced: function () {
                this.isReferenced = true;
            },
            getIsReferenced: function() {
                return !this.currentFileInfo.reference || this.isReferenced;
            },
            getIsOutput: function() {
                return this.evaldCondition;
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.UnicodeDescriptor = function (value) {
            this.value = value;
        };
        tree.UnicodeDescriptor.prototype = {
            type: "UnicodeDescriptor",
            genCSS: function (env, output) {
                output.add(this.value);
            },
            toCSS: tree.toCSS,
            eval: function () { return this; }
        };

    })(require('../tree'));

    (function (tree) {

        tree.URL = function (val, currentFileInfo) {
            this.value = val;
            this.currentFileInfo = currentFileInfo;
        };
        tree.URL.prototype = {
            type: "Url",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            genCSS: function (env, output) {
                output.add("url(");
                this.value.genCSS(env, output);
                output.add(")");
            },
            toCSS: tree.toCSS,
            eval: function (ctx) {
                var val = this.value.eval(ctx), rootpath;

                // Add the base path if the URL is relative
                rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;
                if (rootpath && typeof val.value === "string" && ctx.isPathRelative(val.value)) {
                    if (!val.quote) {
                        rootpath = rootpath.replace(/[\(\)'"\s]/g, function(match) { return "\\"+match; });
                    }
                    val.value = rootpath + val.value;
                }

                val.value = ctx.normalizePath(val.value);

                return new(tree.URL)(val, null);
            }
        };

    })(require('../tree'));

    (function (tree) {

        tree.Value = function (value) {
            this.value = value;
        };
        tree.Value.prototype = {
            type: "Value",
            accept: function (visitor) {
                this.value = visitor.visit(this.value);
            },
            eval: function (env) {
                if (this.value.length === 1) {
                    return this.value[0].eval(env);
                } else {
                    return new(tree.Value)(this.value.map(function (v) {
                        return v.eval(env);
                    }));
                }
            },
            genCSS: function (env, output) {
                var i;
                for(i = 0; i < this.value.length; i++) {
                    this.value[i].genCSS(env, output);
                    if (i+1 < this.value.length) {
                        output.add((env && env.compress) ? ',' : ', ');
                    }
                }
            },
            toCSS: tree.toCSS
        };

    })(require('../tree'));

    (function (tree) {

        tree.Variable = function (name, index, currentFileInfo) {
            this.name = name;
            this.index = index;
            this.currentFileInfo = currentFileInfo;
        };
        tree.Variable.prototype = {
            type: "Variable",
            eval: function (env) {
                var variable, v, name = this.name;

                if (name.indexOf('@@') === 0) {
                    name = '@' + new(tree.Variable)(name.slice(1)).eval(env).value;
                }

                if (this.evaluating) {
                    throw { type: 'Name',
                        message: "Recursive variable definition for " + name,
                        filename: this.currentFileInfo.file,
                        index: this.index };
                }

                this.evaluating = true;

                if (variable = tree.find(env.frames, function (frame) {
                    if (v = frame.variable(name)) {
                        return v.value.eval(env);
                    }
                })) {
                    this.evaluating = false;
                    return variable;
                }
                else {
                    throw { type: 'Name',
                        message: "variable " + name + " is undefined",
                        filename: this.currentFileInfo.filename,
                        index: this.index };
                }
            }
        };

    })(require('../tree'));

    (function (tree) {

        var parseCopyProperties = [
            'paths',            // option - unmodified - paths to search for imports on
            'optimization',     // option - optimization level (for the chunker)
            'files',            // list of files that have been imported, used for import-once
            'contents',         // browser-only, contents of all the files
            'relativeUrls',     // option - whether to adjust URL's to be relative
            'rootpath',         // option - rootpath to append to URL's
            'strictImports',    // option -
            'insecure',         // option - whether to allow imports from insecure ssl hosts
            'dumpLineNumbers',  // option - whether to dump line numbers
            'compress',         // option - whether to compress
            'processImports',   // option - whether to process imports. if false then imports will not be imported
            'syncImport',       // option - whether to import synchronously
            'javascriptEnabled',// option - whether JavaScript is enabled. if undefined, defaults to true
            'mime',             // browser only - mime type for sheet import
            'useFileCache',     // browser only - whether to use the per file session cache
            'currentFileInfo'   // information about the current file - for error reporting and importing and making urls relative etc.
        ];

        //currentFileInfo = {
        //  'relativeUrls' - option - whether to adjust URL's to be relative
        //  'filename' - full resolved filename of current file
        //  'rootpath' - path to append to normal URLs for this node
        //  'currentDirectory' - path to the current file, absolute
        //  'rootFilename' - filename of the base file
        //  'entryPath' - absolute path to the entry file
        //  'reference' - whether the file should not be output and only output parts that are referenced

        tree.parseEnv = function(options) {
            copyFromOriginal(options, this, parseCopyProperties);

            if (!this.contents) { this.contents = {}; }
            if (!this.files) { this.files = {}; }

            if (!this.currentFileInfo) {
                var filename = (options && options.filename) || "input";
                var entryPath = filename.replace(/[^\/\\]*$/, "");
                if (options) {
                    options.filename = null;
                }
                this.currentFileInfo = {
                    filename: filename,
                    relativeUrls: this.relativeUrls,
                    rootpath: (options && options.rootpath) || "",
                    currentDirectory: entryPath,
                    entryPath: entryPath,
                    rootFilename: filename
                };
            }
        };

        var evalCopyProperties = [
            'silent',      // whether to swallow errors and warnings
            'verbose',     // whether to log more activity
            'compress',    // whether to compress
            'yuicompress', // whether to compress with the outside tool yui compressor
            'ieCompat',    // whether to enforce IE compatibility (IE8 data-uri)
            'strictMath',  // whether math has to be within parenthesis
            'strictUnits', // whether units need to evaluate correctly
            'cleancss',    // whether to compress with clean-css
            'sourceMap',   // whether to output a source map
            'importMultiple'// whether we are currently importing multiple copies
        ];

        tree.evalEnv = function(options, frames) {
            copyFromOriginal(options, this, evalCopyProperties);

            this.frames = frames || [];
        };

        tree.evalEnv.prototype.inParenthesis = function () {
            if (!this.parensStack) {
                this.parensStack = [];
            }
            this.parensStack.push(true);
        };

        tree.evalEnv.prototype.outOfParenthesis = function () {
            this.parensStack.pop();
        };

        tree.evalEnv.prototype.isMathOn = function () {
            return this.strictMath ? (this.parensStack && this.parensStack.length) : true;
        };

        tree.evalEnv.prototype.isPathRelative = function (path) {
            return !/^(?:[a-z-]+:|\/)/.test(path);
        };

        tree.evalEnv.prototype.normalizePath = function( path ) {
            var
                segments = path.split("/").reverse(),
                segment;

            path = [];
            while (segments.length !== 0 ) {
                segment = segments.pop();
                switch( segment ) {
                    case ".":
                        break;
                    case "..":
                        if ((path.length === 0) || (path[path.length - 1] === "..")) {
                            path.push( segment );
                        } else {
                            path.pop();
                        }
                        break;
                    default:
                        path.push( segment );
                        break;
                }
            }

            return path.join("/");
        };

        //todo - do the same for the toCSS env
        //tree.toCSSEnv = function (options) {
        //};

        var copyFromOriginal = function(original, destination, propertiesToCopy) {
            if (!original) { return; }

            for(var i = 0; i < propertiesToCopy.length; i++) {
                if (original.hasOwnProperty(propertiesToCopy[i])) {
                    destination[propertiesToCopy[i]] = original[propertiesToCopy[i]];
                }
            }
        };

    })(require('./tree'));

    (function (tree) {

        tree.visitor = function(implementation) {
            this._implementation = implementation;
        };

        tree.visitor.prototype = {
            visit: function(node) {

                if (node instanceof Array) {
                    return this.visitArray(node);
                }

                if (!node || !node.type) {
                    return node;
                }

                var funcName = "visit" + node.type,
                    func = this._implementation[funcName],
                    visitArgs, newNode;
                if (func) {
                    visitArgs = {visitDeeper: true};
                    newNode = func.call(this._implementation, node, visitArgs);
                    if (this._implementation.isReplacing) {
                        node = newNode;
                    }
                }
                if ((!visitArgs || visitArgs.visitDeeper) && node && node.accept) {
                    node.accept(this);
                }
                funcName = funcName + "Out";
                if (this._implementation[funcName]) {
                    this._implementation[funcName](node);
                }
                return node;
            },
            visitArray: function(nodes) {
                var i, newNodes = [];
                for(i = 0; i < nodes.length; i++) {
                    var evald = this.visit(nodes[i]);
                    if (evald instanceof Array) {
                        evald = this.flatten(evald);
                        newNodes = newNodes.concat(evald);
                    } else {
                        newNodes.push(evald);
                    }
                }
                if (this._implementation.isReplacing) {
                    return newNodes;
                }
                return nodes;
            },
            doAccept: function (node) {
                node.accept(this);
            },
            flatten: function(arr, master) {
                return arr.reduce(this.flattenReduce.bind(this), master || []);
            },
            flattenReduce: function(sum, element) {
                if (element instanceof Array) {
                    sum = this.flatten(element, sum);
                } else {
                    sum.push(element);
                }
                return sum;
            }
        };

    })(require('./tree'));
    (function (tree) {
        tree.importVisitor = function(importer, finish, evalEnv) {
            this._visitor = new tree.visitor(this);
            this._importer = importer;
            this._finish = finish;
            this.env = evalEnv || new tree.evalEnv();
            this.importCount = 0;
        };

        tree.importVisitor.prototype = {
            isReplacing: true,
            run: function (root) {
                var error;
                try {
                    // process the contents
                    this._visitor.visit(root);
                }
                catch(e) {
                    error = e;
                }

                this.isFinished = true;

                if (this.importCount === 0) {
                    this._finish(error);
                }
            },
            visitImport: function (importNode, visitArgs) {
                var importVisitor = this,
                    evaldImportNode,
                    inlineCSS = importNode.options.inline;

                if (!importNode.css || inlineCSS) {

                    try {
                        evaldImportNode = importNode.evalForImport(this.env);
                    } catch(e){
                        if (!e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }
                        // attempt to eval properly and treat as css
                        importNode.css = true;
                        // if that fails, this error will be thrown
                        importNode.error = e;
                    }

                    if (evaldImportNode && (!evaldImportNode.css || inlineCSS)) {
                        importNode = evaldImportNode;
                        this.importCount++;
                        var env = new tree.evalEnv(this.env, this.env.frames.slice(0));

                        if (importNode.options.multiple) {
                            env.importMultiple = true;
                        }

                        this._importer.push(importNode.getPath(), importNode.currentFileInfo, importNode.options, function (e, root, imported, fullPath) {
                            if (e && !e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }

                            if (imported && !env.importMultiple) { importNode.skip = imported; }

                            var subFinish = function(e) {
                                importVisitor.importCount--;

                                if (importVisitor.importCount === 0 && importVisitor.isFinished) {
                                    importVisitor._finish(e);
                                }
                            };

                            if (root) {
                                importNode.root = root;
                                importNode.importedFilename = fullPath;
                                if (!inlineCSS && !importNode.skip) {
                                    new(tree.importVisitor)(importVisitor._importer, subFinish, env)
                                        .run(root);
                                    return;
                                }
                            }

                            subFinish();
                        });
                    }
                }
                visitArgs.visitDeeper = false;
                return importNode;
            },
            visitRule: function (ruleNode, visitArgs) {
                visitArgs.visitDeeper = false;
                return ruleNode;
            },
            visitDirective: function (directiveNode, visitArgs) {
                this.env.frames.unshift(directiveNode);
                return directiveNode;
            },
            visitDirectiveOut: function (directiveNode) {
                this.env.frames.shift();
            },
            visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
                this.env.frames.unshift(mixinDefinitionNode);
                return mixinDefinitionNode;
            },
            visitMixinDefinitionOut: function (mixinDefinitionNode) {
                this.env.frames.shift();
            },
            visitRuleset: function (rulesetNode, visitArgs) {
                this.env.frames.unshift(rulesetNode);
                return rulesetNode;
            },
            visitRulesetOut: function (rulesetNode) {
                this.env.frames.shift();
            },
            visitMedia: function (mediaNode, visitArgs) {
                this.env.frames.unshift(mediaNode.ruleset);
                return mediaNode;
            },
            visitMediaOut: function (mediaNode) {
                this.env.frames.shift();
            }
        };

    })(require('./tree'));
    (function (tree) {
        tree.joinSelectorVisitor = function() {
            this.contexts = [[]];
            this._visitor = new tree.visitor(this);
        };

        tree.joinSelectorVisitor.prototype = {
            run: function (root) {
                return this._visitor.visit(root);
            },
            visitRule: function (ruleNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },

            visitRuleset: function (rulesetNode, visitArgs) {
                var context = this.contexts[this.contexts.length - 1];
                var paths = [];
                this.contexts.push(paths);

                if (! rulesetNode.root) {
                    rulesetNode.selectors = rulesetNode.selectors.filter(function(selector) { return selector.getIsOutput(); });
                    if (rulesetNode.selectors.length === 0) {
                        rulesetNode.rules.length = 0;
                    }
                    rulesetNode.joinSelectors(paths, context, rulesetNode.selectors);
                    rulesetNode.paths = paths;
                }
            },
            visitRulesetOut: function (rulesetNode) {
                this.contexts.length = this.contexts.length - 1;
            },
            visitMedia: function (mediaNode, visitArgs) {
                var context = this.contexts[this.contexts.length - 1];
                mediaNode.rules[0].root = (context.length === 0 || context[0].multiMedia);
            }
        };

    })(require('./tree'));
    (function (tree) {
        tree.toCSSVisitor = function(env) {
            this._visitor = new tree.visitor(this);
            this._env = env;
        };

        tree.toCSSVisitor.prototype = {
            isReplacing: true,
            run: function (root) {
                return this._visitor.visit(root);
            },

            visitRule: function (ruleNode, visitArgs) {
                if (ruleNode.variable) {
                    return [];
                }
                return ruleNode;
            },

            visitMixinDefinition: function (mixinNode, visitArgs) {
                return [];
            },

            visitExtend: function (extendNode, visitArgs) {
                return [];
            },

            visitComment: function (commentNode, visitArgs) {
                if (commentNode.isSilent(this._env)) {
                    return [];
                }
                return commentNode;
            },

            visitMedia: function(mediaNode, visitArgs) {
                mediaNode.accept(this._visitor);
                visitArgs.visitDeeper = false;

                if (!mediaNode.rules.length) {
                    return [];
                }
                return mediaNode;
            },

            visitDirective: function(directiveNode, visitArgs) {
                if (directiveNode.currentFileInfo.reference && !directiveNode.isReferenced) {
                    return [];
                }
                if (directiveNode.name === "@charset") {
                    // Only output the debug info together with subsequent @charset definitions
                    // a comment (or @media statement) before the actual @charset directive would
                    // be considered illegal css as it has to be on the first line
                    if (this.charset) {
                        if (directiveNode.debugInfo) {
                            var comment = new tree.Comment("/* " + directiveNode.toCSS(this._env).replace(/\n/g, "")+" */\n");
                            comment.debugInfo = directiveNode.debugInfo;
                            return this._visitor.visit(comment);
                        }
                        return [];
                    }
                    this.charset = true;
                }
                return directiveNode;
            },

            checkPropertiesInRoot: function(rules) {
                var ruleNode;
                for(var i = 0; i < rules.length; i++) {
                    ruleNode = rules[i];
                    if (ruleNode instanceof tree.Rule && !ruleNode.variable) {
                        throw { message: "properties must be inside selector blocks, they cannot be in the root.",
                            index: ruleNode.index, filename: ruleNode.currentFileInfo ? ruleNode.currentFileInfo.filename : null};
                    }
                }
            },

            visitRuleset: function (rulesetNode, visitArgs) {
                var rule, rulesets = [];
                if (rulesetNode.firstRoot) {
                    this.checkPropertiesInRoot(rulesetNode.rules);
                }
                if (! rulesetNode.root) {

                    rulesetNode.paths = rulesetNode.paths
                        .filter(function(p) {
                            var i;
                            if (p[0].elements[0].combinator.value === ' ') {
                                p[0].elements[0].combinator = new(tree.Combinator)('');
                            }
                            for(i = 0; i < p.length; i++) {
                                if (p[i].getIsReferenced() && p[i].getIsOutput()) {
                                    return true;
                                }
                                return false;
                            }
                        });

                    // Compile rules and rulesets
                    for (var i = 0; i < rulesetNode.rules.length; i++) {
                        rule = rulesetNode.rules[i];

                        if (rule.rules) {
                            // visit because we are moving them out from being a child
                            rulesets.push(this._visitor.visit(rule));
                            rulesetNode.rules.splice(i, 1);
                            i--;
                            continue;
                        }
                    }
                    // accept the visitor to remove rules and refactor itself
                    // then we can decide now whether we want it or not
                    if (rulesetNode.rules.length > 0) {
                        rulesetNode.accept(this._visitor);
                    }
                    visitArgs.visitDeeper = false;

                    this._mergeRules(rulesetNode.rules);
                    this._removeDuplicateRules(rulesetNode.rules);

                    // now decide whether we keep the ruleset
                    if (rulesetNode.rules.length > 0 && rulesetNode.paths.length > 0) {
                        rulesets.splice(0, 0, rulesetNode);
                    }
                } else {
                    rulesetNode.accept(this._visitor);
                    visitArgs.visitDeeper = false;
                    if (rulesetNode.firstRoot || rulesetNode.rules.length > 0) {
                        rulesets.splice(0, 0, rulesetNode);
                    }
                }
                if (rulesets.length === 1) {
                    return rulesets[0];
                }
                return rulesets;
            },

            _removeDuplicateRules: function(rules) {
                // remove duplicates
                var ruleCache = {},
                    ruleList, rule, i;
                for(i = rules.length - 1; i >= 0 ; i--) {
                    rule = rules[i];
                    if (rule instanceof tree.Rule) {
                        if (!ruleCache[rule.name]) {
                            ruleCache[rule.name] = rule;
                        } else {
                            ruleList = ruleCache[rule.name];
                            if (ruleList instanceof tree.Rule) {
                                ruleList = ruleCache[rule.name] = [ruleCache[rule.name].toCSS(this._env)];
                            }
                            var ruleCSS = rule.toCSS(this._env);
                            if (ruleList.indexOf(ruleCSS) !== -1) {
                                rules.splice(i, 1);
                            } else {
                                ruleList.push(ruleCSS);
                            }
                        }
                    }
                }
            },

            _mergeRules: function (rules) {
                var groups = {},
                    parts,
                    rule,
                    key;

                for (var i = 0; i < rules.length; i++) {
                    rule = rules[i];

                    if ((rule instanceof tree.Rule) && rule.merge) {
                        key = [rule.name,
                            rule.important ? "!" : ""].join(",");

                        if (!groups[key]) {
                            parts = groups[key] = [];
                        } else {
                            rules.splice(i--, 1);
                        }

                        parts.push(rule);
                    }
                }

                Object.keys(groups).map(function (k) {
                    parts = groups[k];

                    if (parts.length > 1) {
                        rule = parts[0];

                        rule.value = new (tree.Value)(parts.map(function (p) {
                            return p.value;
                        }));
                    }
                });
            }
        };

    })(require('./tree'));
    (function (tree) {
        /*jshint loopfunc:true */

        tree.extendFinderVisitor = function() {
            this._visitor = new tree.visitor(this);
            this.contexts = [];
            this.allExtendsStack = [[]];
        };

        tree.extendFinderVisitor.prototype = {
            run: function (root) {
                root = this._visitor.visit(root);
                root.allExtends = this.allExtendsStack[0];
                return root;
            },
            visitRule: function (ruleNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitRuleset: function (rulesetNode, visitArgs) {

                if (rulesetNode.root) {
                    return;
                }

                var i, j, extend, allSelectorsExtendList = [], extendList;

                // get &:extend(.a); rules which apply to all selectors in this ruleset
                for(i = 0; i < rulesetNode.rules.length; i++) {
                    if (rulesetNode.rules[i] instanceof tree.Extend) {
                        allSelectorsExtendList.push(rulesetNode.rules[i]);
                        rulesetNode.extendOnEveryPath = true;
                    }
                }

                // now find every selector and apply the extends that apply to all extends
                // and the ones which apply to an individual extend
                for(i = 0; i < rulesetNode.paths.length; i++) {
                    var selectorPath = rulesetNode.paths[i],
                        selector = selectorPath[selectorPath.length-1];
                    extendList = selector.extendList.slice(0).concat(allSelectorsExtendList).map(function(allSelectorsExtend) {
                        return allSelectorsExtend.clone();
                    });
                    for(j = 0; j < extendList.length; j++) {
                        this.foundExtends = true;
                        extend = extendList[j];
                        extend.findSelfSelectors(selectorPath);
                        extend.ruleset = rulesetNode;
                        if (j === 0) { extend.firstExtendOnThisSelectorPath = true; }
                        this.allExtendsStack[this.allExtendsStack.length-1].push(extend);
                    }
                }

                this.contexts.push(rulesetNode.selectors);
            },
            visitRulesetOut: function (rulesetNode) {
                if (!rulesetNode.root) {
                    this.contexts.length = this.contexts.length - 1;
                }
            },
            visitMedia: function (mediaNode, visitArgs) {
                mediaNode.allExtends = [];
                this.allExtendsStack.push(mediaNode.allExtends);
            },
            visitMediaOut: function (mediaNode) {
                this.allExtendsStack.length = this.allExtendsStack.length - 1;
            },
            visitDirective: function (directiveNode, visitArgs) {
                directiveNode.allExtends = [];
                this.allExtendsStack.push(directiveNode.allExtends);
            },
            visitDirectiveOut: function (directiveNode) {
                this.allExtendsStack.length = this.allExtendsStack.length - 1;
            }
        };

        tree.processExtendsVisitor = function() {
            this._visitor = new tree.visitor(this);
        };

        tree.processExtendsVisitor.prototype = {
            run: function(root) {
                var extendFinder = new tree.extendFinderVisitor();
                extendFinder.run(root);
                if (!extendFinder.foundExtends) { return root; }
                root.allExtends = root.allExtends.concat(this.doExtendChaining(root.allExtends, root.allExtends));
                this.allExtendsStack = [root.allExtends];
                return this._visitor.visit(root);
            },
            doExtendChaining: function (extendsList, extendsListTarget, iterationCount) {
                //
                // chaining is different from normal extension.. if we extend an extend then we are not just copying, altering and pasting
                // the selector we would do normally, but we are also adding an extend with the same target selector
                // this means this new extend can then go and alter other extends
                //
                // this method deals with all the chaining work - without it, extend is flat and doesn't work on other extend selectors
                // this is also the most expensive.. and a match on one selector can cause an extension of a selector we had already processed if
                // we look at each selector at a time, as is done in visitRuleset

                var extendIndex, targetExtendIndex, matches, extendsToAdd = [], newSelector, extendVisitor = this, selectorPath, extend, targetExtend, newExtend;

                iterationCount = iterationCount || 0;

                //loop through comparing every extend with every target extend.
                // a target extend is the one on the ruleset we are looking at copy/edit/pasting in place
                // e.g.  .a:extend(.b) {}  and .b:extend(.c) {} then the first extend extends the second one
                // and the second is the target.
                // the seperation into two lists allows us to process a subset of chains with a bigger set, as is the
                // case when processing media queries
                for(extendIndex = 0; extendIndex < extendsList.length; extendIndex++){
                    for(targetExtendIndex = 0; targetExtendIndex < extendsListTarget.length; targetExtendIndex++){

                        extend = extendsList[extendIndex];
                        targetExtend = extendsListTarget[targetExtendIndex];

                        // look for circular references
                        if (this.inInheritanceChain(targetExtend, extend)) { continue; }

                        // find a match in the target extends self selector (the bit before :extend)
                        selectorPath = [targetExtend.selfSelectors[0]];
                        matches = extendVisitor.findMatch(extend, selectorPath);

                        if (matches.length) {

                            // we found a match, so for each self selector..
                            extend.selfSelectors.forEach(function(selfSelector) {

                                // process the extend as usual
                                newSelector = extendVisitor.extendSelector(matches, selectorPath, selfSelector);

                                // but now we create a new extend from it
                                newExtend = new(tree.Extend)(targetExtend.selector, targetExtend.option, 0);
                                newExtend.selfSelectors = newSelector;

                                // add the extend onto the list of extends for that selector
                                newSelector[newSelector.length-1].extendList = [newExtend];

                                // record that we need to add it.
                                extendsToAdd.push(newExtend);
                                newExtend.ruleset = targetExtend.ruleset;

                                //remember its parents for circular references
                                newExtend.parents = [targetExtend, extend];

                                // only process the selector once.. if we have :extend(.a,.b) then multiple
                                // extends will look at the same selector path, so when extending
                                // we know that any others will be duplicates in terms of what is added to the css
                                if (targetExtend.firstExtendOnThisSelectorPath) {
                                    newExtend.firstExtendOnThisSelectorPath = true;
                                    targetExtend.ruleset.paths.push(newSelector);
                                }
                            });
                        }
                    }
                }

                if (extendsToAdd.length) {
                    // try to detect circular references to stop a stack overflow.
                    // may no longer be needed.
                    this.extendChainCount++;
                    if (iterationCount > 100) {
                        var selectorOne = "{unable to calculate}";
                        var selectorTwo = "{unable to calculate}";
                        try
                        {
                            selectorOne = extendsToAdd[0].selfSelectors[0].toCSS();
                            selectorTwo = extendsToAdd[0].selector.toCSS();
                        }
                        catch(e) {}
                        throw {message: "extend circular reference detected. One of the circular extends is currently:"+selectorOne+":extend(" + selectorTwo+")"};
                    }

                    // now process the new extends on the existing rules so that we can handle a extending b extending c ectending d extending e...
                    return extendsToAdd.concat(extendVisitor.doExtendChaining(extendsToAdd, extendsListTarget, iterationCount+1));
                } else {
                    return extendsToAdd;
                }
            },
            inInheritanceChain: function (possibleParent, possibleChild) {
                if (possibleParent === possibleChild) {
                    return true;
                }
                if (possibleChild.parents) {
                    if (this.inInheritanceChain(possibleParent, possibleChild.parents[0])) {
                        return true;
                    }
                    if (this.inInheritanceChain(possibleParent, possibleChild.parents[1])) {
                        return true;
                    }
                }
                return false;
            },
            visitRule: function (ruleNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitSelector: function (selectorNode, visitArgs) {
                visitArgs.visitDeeper = false;
            },
            visitRuleset: function (rulesetNode, visitArgs) {
                if (rulesetNode.root) {
                    return;
                }
                var matches, pathIndex, extendIndex, allExtends = this.allExtendsStack[this.allExtendsStack.length-1], selectorsToAdd = [], extendVisitor = this, selectorPath;

                // look at each selector path in the ruleset, find any extend matches and then copy, find and replace

                for(extendIndex = 0; extendIndex < allExtends.length; extendIndex++) {
                    for(pathIndex = 0; pathIndex < rulesetNode.paths.length; pathIndex++) {

                        selectorPath = rulesetNode.paths[pathIndex];

                        // extending extends happens initially, before the main pass
                        if (rulesetNode.extendOnEveryPath || selectorPath[selectorPath.length-1].extendList.length) { continue; }

                        matches = this.findMatch(allExtends[extendIndex], selectorPath);

                        if (matches.length) {

                            allExtends[extendIndex].selfSelectors.forEach(function(selfSelector) {
                                selectorsToAdd.push(extendVisitor.extendSelector(matches, selectorPath, selfSelector));
                            });
                        }
                    }
                }
                rulesetNode.paths = rulesetNode.paths.concat(selectorsToAdd);
            },
            findMatch: function (extend, haystackSelectorPath) {
                //
                // look through the haystack selector path to try and find the needle - extend.selector
                // returns an array of selector matches that can then be replaced
                //
                var haystackSelectorIndex, hackstackSelector, hackstackElementIndex, haystackElement,
                    targetCombinator, i,
                    extendVisitor = this,
                    needleElements = extend.selector.elements,
                    potentialMatches = [], potentialMatch, matches = [];

                // loop through the haystack elements
                for(haystackSelectorIndex = 0; haystackSelectorIndex < haystackSelectorPath.length; haystackSelectorIndex++) {
                    hackstackSelector = haystackSelectorPath[haystackSelectorIndex];

                    for(hackstackElementIndex = 0; hackstackElementIndex < hackstackSelector.elements.length; hackstackElementIndex++) {

                        haystackElement = hackstackSelector.elements[hackstackElementIndex];

                        // if we allow elements before our match we can add a potential match every time. otherwise only at the first element.
                        if (extend.allowBefore || (haystackSelectorIndex === 0 && hackstackElementIndex === 0)) {
                            potentialMatches.push({pathIndex: haystackSelectorIndex, index: hackstackElementIndex, matched: 0, initialCombinator: haystackElement.combinator});
                        }

                        for(i = 0; i < potentialMatches.length; i++) {
                            potentialMatch = potentialMatches[i];

                            // selectors add " " onto the first element. When we use & it joins the selectors together, but if we don't
                            // then each selector in haystackSelectorPath has a space before it added in the toCSS phase. so we need to work out
                            // what the resulting combinator will be
                            targetCombinator = haystackElement.combinator.value;
                            if (targetCombinator === '' && hackstackElementIndex === 0) {
                                targetCombinator = ' ';
                            }

                            // if we don't match, null our match to indicate failure
                            if (!extendVisitor.isElementValuesEqual(needleElements[potentialMatch.matched].value, haystackElement.value) ||
                                (potentialMatch.matched > 0 && needleElements[potentialMatch.matched].combinator.value !== targetCombinator)) {
                                potentialMatch = null;
                            } else {
                                potentialMatch.matched++;
                            }

                            // if we are still valid and have finished, test whether we have elements after and whether these are allowed
                            if (potentialMatch) {
                                potentialMatch.finished = potentialMatch.matched === needleElements.length;
                                if (potentialMatch.finished &&
                                    (!extend.allowAfter && (hackstackElementIndex+1 < hackstackSelector.elements.length || haystackSelectorIndex+1 < haystackSelectorPath.length))) {
                                    potentialMatch = null;
                                }
                            }
                            // if null we remove, if not, we are still valid, so either push as a valid match or continue
                            if (potentialMatch) {
                                if (potentialMatch.finished) {
                                    potentialMatch.length = needleElements.length;
                                    potentialMatch.endPathIndex = haystackSelectorIndex;
                                    potentialMatch.endPathElementIndex = hackstackElementIndex + 1; // index after end of match
                                    potentialMatches.length = 0; // we don't allow matches to overlap, so start matching again
                                    matches.push(potentialMatch);
                                }
                            } else {
                                potentialMatches.splice(i, 1);
                                i--;
                            }
                        }
                    }
                }
                return matches;
            },
            isElementValuesEqual: function(elementValue1, elementValue2) {
                if (typeof elementValue1 === "string" || typeof elementValue2 === "string") {
                    return elementValue1 === elementValue2;
                }
                if (elementValue1 instanceof tree.Attribute) {
                    if (elementValue1.op !== elementValue2.op || elementValue1.key !== elementValue2.key) {
                        return false;
                    }
                    if (!elementValue1.value || !elementValue2.value) {
                        if (elementValue1.value || elementValue2.value) {
                            return false;
                        }
                        return true;
                    }
                    elementValue1 = elementValue1.value.value || elementValue1.value;
                    elementValue2 = elementValue2.value.value || elementValue2.value;
                    return elementValue1 === elementValue2;
                }
                elementValue1 = elementValue1.value;
                elementValue2 = elementValue2.value;
                if (elementValue1 instanceof tree.Selector) {
                    if (!(elementValue2 instanceof tree.Selector) || elementValue1.elements.length !== elementValue2.elements.length) {
                        return false;
                    }
                    for(var i = 0; i <elementValue1.elements.length; i++) {
                        if (elementValue1.elements[i].combinator.value !== elementValue2.elements[i].combinator.value) {
                            if (i !== 0 || (elementValue1.elements[i].combinator.value || ' ') !== (elementValue2.elements[i].combinator.value || ' ')) {
                                return false;
                            }
                        }
                        if (!this.isElementValuesEqual(elementValue1.elements[i].value, elementValue2.elements[i].value)) {
                            return false;
                        }
                    }
                    return true;
                }
                return false;
            },
            extendSelector:function (matches, selectorPath, replacementSelector) {

                //for a set of matches, replace each match with the replacement selector

                var currentSelectorPathIndex = 0,
                    currentSelectorPathElementIndex = 0,
                    path = [],
                    matchIndex,
                    selector,
                    firstElement,
                    match,
                    newElements;

                for (matchIndex = 0; matchIndex < matches.length; matchIndex++) {
                    match = matches[matchIndex];
                    selector = selectorPath[match.pathIndex];
                    firstElement = new tree.Element(
                        match.initialCombinator,
                        replacementSelector.elements[0].value,
                        replacementSelector.elements[0].index,
                        replacementSelector.elements[0].currentFileInfo
                    );

                    if (match.pathIndex > currentSelectorPathIndex && currentSelectorPathElementIndex > 0) {
                        path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                        currentSelectorPathElementIndex = 0;
                        currentSelectorPathIndex++;
                    }

                    newElements = selector.elements
                        .slice(currentSelectorPathElementIndex, match.index)
                        .concat([firstElement])
                        .concat(replacementSelector.elements.slice(1));

                    if (currentSelectorPathIndex === match.pathIndex && matchIndex > 0) {
                        path[path.length - 1].elements =
                            path[path.length - 1].elements.concat(newElements);
                    } else {
                        path = path.concat(selectorPath.slice(currentSelectorPathIndex, match.pathIndex));

                        path.push(new tree.Selector(
                            newElements
                        ));
                    }
                    currentSelectorPathIndex = match.endPathIndex;
                    currentSelectorPathElementIndex = match.endPathElementIndex;
                    if (currentSelectorPathElementIndex >= selectorPath[currentSelectorPathIndex].elements.length) {
                        currentSelectorPathElementIndex = 0;
                        currentSelectorPathIndex++;
                    }
                }

                if (currentSelectorPathIndex < selectorPath.length && currentSelectorPathElementIndex > 0) {
                    path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                    currentSelectorPathIndex++;
                }

                path = path.concat(selectorPath.slice(currentSelectorPathIndex, selectorPath.length));

                return path;
            },
            visitRulesetOut: function (rulesetNode) {
            },
            visitMedia: function (mediaNode, visitArgs) {
                var newAllExtends = mediaNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
                newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, mediaNode.allExtends));
                this.allExtendsStack.push(newAllExtends);
            },
            visitMediaOut: function (mediaNode) {
                this.allExtendsStack.length = this.allExtendsStack.length - 1;
            },
            visitDirective: function (directiveNode, visitArgs) {
                var newAllExtends = directiveNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
                newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, directiveNode.allExtends));
                this.allExtendsStack.push(newAllExtends);
            },
            visitDirectiveOut: function (directiveNode) {
                this.allExtendsStack.length = this.allExtendsStack.length - 1;
            }
        };

    })(require('./tree'));

    (function (tree) {

        tree.sourceMapOutput = function (options) {
            this._css = [];
            this._rootNode = options.rootNode;
            this._writeSourceMap = options.writeSourceMap;
            this._contentsMap = options.contentsMap;
            this._sourceMapFilename = options.sourceMapFilename;
            this._outputFilename = options.outputFilename;
            this._sourceMapBasepath = options.sourceMapBasepath;
            this._sourceMapRootpath = options.sourceMapRootpath;
            this._outputSourceFiles = options.outputSourceFiles;
            this._sourceMapGeneratorConstructor = options.sourceMapGenerator || require("source-map").SourceMapGenerator;

            if (this._sourceMapRootpath && this._sourceMapRootpath.charAt(this._sourceMapRootpath.length-1) !== '/') {
                this._sourceMapRootpath += '/';
            }

            this._lineNumber = 0;
            this._column = 0;
        };

        tree.sourceMapOutput.prototype.normalizeFilename = function(filename) {
            if (this._sourceMapBasepath && filename.indexOf(this._sourceMapBasepath) === 0) {
                filename = filename.substring(this._sourceMapBasepath.length);
                if (filename.charAt(0) === '\\' || filename.charAt(0) === '/') {
                    filename = filename.substring(1);
                }
            }
            return (this._sourceMapRootpath || "") + filename.replace(/\\/g, '/');
        };

        tree.sourceMapOutput.prototype.add = function(chunk, fileInfo, index, mapLines) {

            //ignore adding empty strings
            if (!chunk) {
                return;
            }

            var lines,
                sourceLines,
                columns,
                sourceColumns,
                i;

            if (fileInfo) {
                var inputSource = this._contentsMap[fileInfo.filename].substring(0, index);
                sourceLines = inputSource.split("\n");
                sourceColumns = sourceLines[sourceLines.length-1];
            }

            lines = chunk.split("\n");
            columns = lines[lines.length-1];

            if (fileInfo) {
                if (!mapLines) {
                    this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + 1, column: this._column},
                        original: { line: sourceLines.length, column: sourceColumns.length},
                        source: this.normalizeFilename(fileInfo.filename)});
                } else {
                    for(i = 0; i < lines.length; i++) {
                        this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + i + 1, column: i === 0 ? this._column : 0},
                            original: { line: sourceLines.length + i, column: i === 0 ? sourceColumns.length : 0},
                            source: this.normalizeFilename(fileInfo.filename)});
                    }
                }
            }

            if (lines.length === 1) {
                this._column += columns.length;
            } else {
                this._lineNumber += lines.length - 1;
                this._column = columns.length;
            }

            this._css.push(chunk);
        };

        tree.sourceMapOutput.prototype.isEmpty = function() {
            return this._css.length === 0;
        };

        tree.sourceMapOutput.prototype.toCSS = function(env) {
            this._sourceMapGenerator = new this._sourceMapGeneratorConstructor({ file: this._outputFilename, sourceRoot: null });

            if (this._outputSourceFiles) {
                for(var filename in this._contentsMap) {
                    this._sourceMapGenerator.setSourceContent(this.normalizeFilename(filename), this._contentsMap[filename]);
                }
            }

            this._rootNode.genCSS(env, this);

            if (this._css.length > 0) {
                var sourceMapFilename,
                    sourceMapContent = JSON.stringify(this._sourceMapGenerator.toJSON());

                if (this._sourceMapFilename) {
                    sourceMapFilename = this.normalizeFilename(this._sourceMapFilename);
                }

                if (this._writeSourceMap) {
                    this._writeSourceMap(sourceMapContent);
                } else {
                    sourceMapFilename = "data:application/json," + encodeURIComponent(sourceMapContent);
                }

                if (sourceMapFilename) {
                    this._css.push("/*# sourceMappingURL=" + sourceMapFilename + " */");
                }
            }

            return this._css.join('');
        };

    })(require('./tree'));

//
// browser.js - client-side engine
//
    /*global less, window, document, XMLHttpRequest, location */

    var isFileProtocol = /^(file|chrome(-extension)?|resource|qrc|app):/.test(location.protocol);

    less.env = less.env || (location.hostname == '127.0.0.1' ||
        location.hostname == '0.0.0.0'   ||
        location.hostname == 'localhost' ||
        location.port.length > 0         ||
        isFileProtocol                   ? 'development'
        : 'production');

    var logLevel = {
        info: 2,
        errors: 1,
        none: 0
    };

// The amount of logging in the javascript console.
// 2 - Information and errors
// 1 - Errors
// 0 - None
// Defaults to 2
    less.logLevel = typeof(less.logLevel) != 'undefined' ? less.logLevel : logLevel.info;

// Load styles asynchronously (default: false)
//
// This is set to `false` by default, so that the body
// doesn't start loading before the stylesheets are parsed.
// Setting this to `true` can result in flickering.
//
    less.async = less.async || false;
    less.fileAsync = less.fileAsync || false;

// Interval between watch polls
    less.poll = less.poll || (isFileProtocol ? 1000 : 1500);

//Setup user functions
    if (less.functions) {
        for(var func in less.functions) {
            less.tree.functions[func] = less.functions[func];
        }
    }

    var dumpLineNumbers = /!dumpLineNumbers:(comments|mediaquery|all)/.exec(location.hash);
    if (dumpLineNumbers) {
        less.dumpLineNumbers = dumpLineNumbers[1];
    }

    var typePattern = /^text\/(x-)?less$/;
    var cache = null;
    var fileCache = {};

    function log(str, level) {
        if (less.env == 'development' && typeof(console) !== 'undefined' && less.logLevel >= level) {
            console.log('less: ' + str);
        }
    }

    function extractId(href) {
        return href.replace(/^[a-z-]+:\/+?[^\/]+/, '' )  // Remove protocol & domain
            .replace(/^\//,                 '' )  // Remove root /
            .replace(/\.[a-zA-Z]+$/,        '' )  // Remove simple extension
            .replace(/[^\.\w-]+/g,          '-')  // Replace illegal characters
            .replace(/\./g,                 ':'); // Replace dots with colons(for valid id)
    }

    function errorConsole(e, rootHref) {
        var template = '{line} {content}';
        var filename = e.filename || rootHref;
        var errors = [];
        var content = (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
            " in " + filename + " ";

        var errorline = function (e, i, classname) {
            if (e.extract[i] !== undefined) {
                errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                    .replace(/\{class\}/, classname)
                    .replace(/\{content\}/, e.extract[i]));
            }
        };

        if (e.extract) {
            errorline(e, 0, '');
            errorline(e, 1, 'line');
            errorline(e, 2, '');
            content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':\n' +
                errors.join('\n');
        } else if (e.stack) {
            content += e.stack;
        }
        log(content, logLevel.errors);
    }

    function createCSS(styles, sheet, lastModified) {
        // Strip the query-string
        var href = sheet.href || '';

        // If there is no title set, use the filename, minus the extension
        var id = 'less:' + (sheet.title || extractId(href));

        // If this has already been inserted into the DOM, we may need to replace it
        var oldCss = document.getElementById(id);
        var keepOldCss = false;

        // Create a new stylesheet node for insertion or (if necessary) replacement
        var css = document.createElement('style');
        css.setAttribute('type', 'text/css');
        if (sheet.media) {
            css.setAttribute('media', sheet.media);
        }
        css.id = id;

        if (css.styleSheet) { // IE
            try {
                css.styleSheet.cssText = styles;
            } catch (e) {
                throw new(Error)("Couldn't reassign styleSheet.cssText.");
            }
        } else {
            css.appendChild(document.createTextNode(styles));

            // If new contents match contents of oldCss, don't replace oldCss
            keepOldCss = (oldCss !== null && oldCss.childNodes.length > 0 && css.childNodes.length > 0 &&
                oldCss.firstChild.nodeValue === css.firstChild.nodeValue);
        }

        var head = document.getElementsByTagName('head')[0];

        // If there is no oldCss, just append; otherwise, only append if we need
        // to replace oldCss with an updated stylesheet
        if (oldCss === null || keepOldCss === false) {
            var nextEl = sheet && sheet.nextSibling || null;
            if (nextEl) {
                nextEl.parentNode.insertBefore(css, nextEl);
            } else {
                head.appendChild(css);
            }
        }
        if (oldCss && keepOldCss === false) {
            oldCss.parentNode.removeChild(oldCss);
        }

        // Don't update the local store if the file wasn't modified
        if (lastModified && cache) {
            log('saving ' + href + ' to cache.', logLevel.info);
            try {
                cache.setItem(href, styles);
                cache.setItem(href + ':timestamp', lastModified);
            } catch(e) {
                //TODO - could do with adding more robust error handling
                log('failed to save', logLevel.errors);
            }
        }
    }

    function errorHTML(e, rootHref) {
        var id = 'less-error-message:' + extractId(rootHref || "");
        var template = '<li><label>{line}</label><pre class="{class}">{content}</pre></li>';
        var elem = document.createElement('div'), timer, content, errors = [];
        var filename = e.filename || rootHref;
        var filenameNoPath = filename.match(/([^\/]+(\?.*)?)$/)[1];

        elem.id        = id;
        elem.className = "less-error-message";

        content = '<h3>'  + (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
            '</h3>' + '<p>in <a href="' + filename   + '">' + filenameNoPath + "</a> ";

        var errorline = function (e, i, classname) {
            if (e.extract[i] !== undefined) {
                errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                    .replace(/\{class\}/, classname)
                    .replace(/\{content\}/, e.extract[i]));
            }
        };

        if (e.extract) {
            errorline(e, 0, '');
            errorline(e, 1, 'line');
            errorline(e, 2, '');
            content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':</p>' +
                '<ul>' + errors.join('') + '</ul>';
        } else if (e.stack) {
            content += '<br/>' + e.stack.split('\n').slice(1).join('<br/>');
        }
        elem.innerHTML = content;

        // CSS for error messages
        createCSS([
            '.less-error-message ul, .less-error-message li {',
            'list-style-type: none;',
            'margin-right: 15px;',
            'padding: 4px 0;',
            'margin: 0;',
            '}',
            '.less-error-message label {',
            'font-size: 12px;',
            'margin-right: 15px;',
            'padding: 4px 0;',
            'color: #cc7777;',
            '}',
            '.less-error-message pre {',
            'color: #dd6666;',
            'padding: 4px 0;',
            'margin: 0;',
            'display: inline-block;',
            '}',
            '.less-error-message pre.line {',
            'color: #ff0000;',
            '}',
            '.less-error-message h3 {',
            'font-size: 20px;',
            'font-weight: bold;',
            'padding: 15px 0 5px 0;',
            'margin: 0;',
            '}',
            '.less-error-message a {',
            'color: #10a',
            '}',
            '.less-error-message .error {',
            'color: red;',
            'font-weight: bold;',
            'padding-bottom: 2px;',
            'border-bottom: 1px dashed red;',
            '}'
        ].join('\n'), { title: 'error-message' });

        elem.style.cssText = [
            "font-family: Arial, sans-serif",
            "border: 1px solid #e00",
            "background-color: #eee",
            "border-radius: 5px",
            "-webkit-border-radius: 5px",
            "-moz-border-radius: 5px",
            "color: #e00",
            "padding: 15px",
            "margin-bottom: 15px"
        ].join(';');

        if (less.env == 'development') {
            timer = setInterval(function () {
                if (document.body) {
                    if (document.getElementById(id)) {
                        document.body.replaceChild(elem, document.getElementById(id));
                    } else {
                        document.body.insertBefore(elem, document.body.firstChild);
                    }
                    clearInterval(timer);
                }
            }, 10);
        }
    }

    function error(e, rootHref) {
        if (!less.errorReporting || less.errorReporting === "html") {
            errorHTML(e, rootHref);
        } else if (less.errorReporting === "console") {
            errorConsole(e, rootHref);
        } else if (typeof less.errorReporting === 'function') {
            less.errorReporting("add", e, rootHref);
        }
    }

    function removeErrorHTML(path) {
        var node = document.getElementById('less-error-message:' + extractId(path));
        if (node) {
            node.parentNode.removeChild(node);
        }
    }

    function removeErrorConsole(path) {
        //no action
    }

    function removeError(path) {
        if (!less.errorReporting || less.errorReporting === "html") {
            removeErrorHTML(path);
        } else if (less.errorReporting === "console") {
            removeErrorConsole(path);
        } else if (typeof less.errorReporting === 'function') {
            less.errorReporting("remove", path);
        }
    }

    function loadStyles(newVars) {
        var styles = document.getElementsByTagName('style'),
            style;
        for (var i = 0; i < styles.length; i++) {
            style = styles[i];
            if (style.type.match(typePattern)) {
                var env = new less.tree.parseEnv(less),
                    lessText = style.innerHTML || '';
                env.filename = document.location.href.replace(/#.*$/, '');
                if (newVars) {
                    env.useFileCache = true;
                    lessText += "\n" + newVars;
                }

                /*jshint loopfunc:true */
                // use closure to store current value of i
                var callback = (function(style) {
                    return function (e, cssAST) {
                        if (e) {
                            return error(e, "inline");
                        }
                        var css = cssAST.toCSS(less);
                        style.type = 'text/css';
                        if (style.styleSheet) {
                            style.styleSheet.cssText = css;
                        } else {
                            style.innerHTML = css;
                        }
                    };
                })(style);
                new(less.Parser)(env).parse(lessText, callback);
            }
        }
    }

    function extractUrlParts(url, baseUrl) {
        // urlParts[1] = protocol&hostname || /
        // urlParts[2] = / if path relative to host base
        // urlParts[3] = directories
        // urlParts[4] = filename
        // urlParts[5] = parameters

        var urlPartsRegex = /^((?:[a-z-]+:)?\/+?(?:[^\/\?#]*\/)|([\/\\]))?((?:[^\/\\\?#]*[\/\\])*)([^\/\\\?#]*)([#\?].*)?$/i,
            urlParts = url.match(urlPartsRegex),
            returner = {}, directories = [], i, baseUrlParts;

        if (!urlParts) {
            throw new Error("Could not parse sheet href - '"+url+"'");
        }

        // Stylesheets in IE don't always return the full path
        if (!urlParts[1] || urlParts[2]) {
            baseUrlParts = baseUrl.match(urlPartsRegex);
            if (!baseUrlParts) {
                throw new Error("Could not parse page url - '"+baseUrl+"'");
            }
            urlParts[1] = urlParts[1] || baseUrlParts[1] || "";
            if (!urlParts[2]) {
                urlParts[3] = baseUrlParts[3] + urlParts[3];
            }
        }

        if (urlParts[3]) {
            directories = urlParts[3].replace(/\\/g, "/").split("/");

            // extract out . before .. so .. doesn't absorb a non-directory
            for(i = 0; i < directories.length; i++) {
                if (directories[i] === ".") {
                    directories.splice(i, 1);
                    i -= 1;
                }
            }

            for(i = 0; i < directories.length; i++) {
                if (directories[i] === ".." && i > 0) {
                    directories.splice(i-1, 2);
                    i -= 2;
                }
            }
        }

        returner.hostPart = urlParts[1];
        returner.directories = directories;
        returner.path = urlParts[1] + directories.join("/");
        returner.fileUrl = returner.path + (urlParts[4] || "");
        returner.url = returner.fileUrl + (urlParts[5] || "");
        return returner;
    }

    function pathDiff(url, baseUrl) {
        // diff between two paths to create a relative path

        var urlParts = extractUrlParts(url),
            baseUrlParts = extractUrlParts(baseUrl),
            i, max, urlDirectories, baseUrlDirectories, diff = "";
        if (urlParts.hostPart !== baseUrlParts.hostPart) {
            return "";
        }
        max = Math.max(baseUrlParts.directories.length, urlParts.directories.length);
        for(i = 0; i < max; i++) {
            if (baseUrlParts.directories[i] !== urlParts.directories[i]) { break; }
        }
        baseUrlDirectories = baseUrlParts.directories.slice(i);
        urlDirectories = urlParts.directories.slice(i);
        for(i = 0; i < baseUrlDirectories.length-1; i++) {
            diff += "../";
        }
        for(i = 0; i < urlDirectories.length-1; i++) {
            diff += urlDirectories[i] + "/";
        }
        return diff;
    }

    function getXMLHttpRequest() {
        if (window.XMLHttpRequest) {
            return new XMLHttpRequest();
        } else {
            try {
                /*global ActiveXObject */
                return new ActiveXObject("MSXML2.XMLHTTP.3.0");
            } catch (e) {
                log("browser doesn't support AJAX.", logLevel.errors);
                return null;
            }
        }
    }

    function doXHR(url, type, callback, errback) {
        var xhr = getXMLHttpRequest();
        var async = isFileProtocol ? less.fileAsync : less.async;

        if (typeof(xhr.overrideMimeType) === 'function') {
            xhr.overrideMimeType('text/css');
        }
        log("XHR: Getting '" + url + "'", logLevel.info);
        xhr.open('GET', url, async);
        xhr.setRequestHeader('Accept', type || 'text/x-less, text/css; q=0.9, */*; q=0.5');
        xhr.send(null);

        function handleResponse(xhr, callback, errback) {
            if (xhr.status >= 200 && xhr.status < 300) {
                callback(xhr.responseText,
                    xhr.getResponseHeader("Last-Modified"));
            } else if (typeof(errback) === 'function') {
                errback(xhr.status, url);
            }
        }

        if (isFileProtocol && !less.fileAsync) {
            if (xhr.status === 0 || (xhr.status >= 200 && xhr.status < 300)) {
                callback(xhr.responseText);
            } else {
                errback(xhr.status, url);
            }
        } else if (async) {
            xhr.onreadystatechange = function () {
                if (xhr.readyState == 4) {
                    handleResponse(xhr, callback, errback);
                }
            };
        } else {
            handleResponse(xhr, callback, errback);
        }
    }

    function loadFile(originalHref, currentFileInfo, callback, env, newVars) {

        if (currentFileInfo && currentFileInfo.currentDirectory && !/^([a-z-]+:)?\//.test(originalHref)) {
            originalHref = currentFileInfo.currentDirectory + originalHref;
        }

        // sheet may be set to the stylesheet for the initial load or a collection of properties including
        // some env variables for imports
        var hrefParts = extractUrlParts(originalHref, window.location.href);
        var href      = hrefParts.url;
        var newFileInfo = {
            currentDirectory: hrefParts.path,
            filename: href
        };

        if (currentFileInfo) {
            newFileInfo.entryPath = currentFileInfo.entryPath;
            newFileInfo.rootpath = currentFileInfo.rootpath;
            newFileInfo.rootFilename = currentFileInfo.rootFilename;
            newFileInfo.relativeUrls = currentFileInfo.relativeUrls;
        } else {
            newFileInfo.entryPath = hrefParts.path;
            newFileInfo.rootpath = less.rootpath || hrefParts.path;
            newFileInfo.rootFilename = href;
            newFileInfo.relativeUrls = env.relativeUrls;
        }

        if (newFileInfo.relativeUrls) {
            if (env.rootpath) {
                newFileInfo.rootpath = extractUrlParts(env.rootpath + pathDiff(hrefParts.path, newFileInfo.entryPath)).path;
            } else {
                newFileInfo.rootpath = hrefParts.path;
            }
        }

        if (env.useFileCache && fileCache[href]) {
            try {
                var lessText = fileCache[href];
                if (newVars) {
                    lessText += "\n" + newVars;
                }
                callback(null, lessText, href, newFileInfo, { lastModified: new Date() });
            } catch (e) {
                callback(e, null, href);
            }
            return;
        }

        doXHR(href, env.mime, function (data, lastModified) {
            // per file cache
            fileCache[href] = data;

            // Use remote copy (re-parse)
            try {
                callback(null, data, href, newFileInfo, { lastModified: lastModified });
            } catch (e) {
                callback(e, null, href);
            }
        }, function (status, url) {
            callback({ type: 'File', message: "'" + url + "' wasn't found (" + status + ")" }, null, href);
        });
    }

    function loadStyleSheet(sheet, callback, reload, remaining, newVars) {

        var env = new less.tree.parseEnv(less);
        env.mime = sheet.type;

        if (newVars) {
            env.useFileCache = true;
        }

        loadFile(sheet.href, null, function(e, data, path, newFileInfo, webInfo) {

            if (webInfo) {
                webInfo.remaining = remaining;

                var css       = cache && cache.getItem(path),
                    timestamp = cache && cache.getItem(path + ':timestamp');

                if (!reload && timestamp && webInfo.lastModified &&
                    (new(Date)(webInfo.lastModified).valueOf() ===
                        new(Date)(timestamp).valueOf())) {
                    // Use local copy
                    createCSS(css, sheet);
                    webInfo.local = true;
                    callback(null, null, data, sheet, webInfo, path);
                    return;
                }
            }

            //TODO add tests around how this behaves when reloading
            removeError(path);

            if (data) {
                env.currentFileInfo = newFileInfo;
                new(less.Parser)(env).parse(data, function (e, root) {
                    if (e) { return callback(e, null, null, sheet); }
                    try {
                        callback(e, root, data, sheet, webInfo, path);
                    } catch (e) {
                        callback(e, null, null, sheet);
                    }
                });
            } else {
                callback(e, null, null, sheet, webInfo, path);
            }
        }, env, newVars);
    }

    function loadStyleSheets(callback, reload, newVars) {
        for (var i = 0; i < less.sheets.length; i++) {
            loadStyleSheet(less.sheets[i], callback, reload, less.sheets.length - (i + 1), newVars);
        }
    }

    function initRunningMode(){
        if (less.env === 'development') {
            less.optimization = 0;
            less.watchTimer = setInterval(function () {
                if (less.watchMode) {
                    loadStyleSheets(function (e, root, _, sheet, env) {
                        if (e) {
                            error(e, sheet.href);
                        } else if (root) {
                            createCSS(root.toCSS(less), sheet, env.lastModified);
                        }
                    });
                }
            }, less.poll);
        } else {
            less.optimization = 3;
        }
    }

//
// Watch mode
//
    less.watch   = function () {
        if (!less.watchMode ){
            less.env = 'development';
            initRunningMode();
        }
        return this.watchMode = true;
    };

    less.unwatch = function () {clearInterval(less.watchTimer); return this.watchMode = false; };

    if (/!watch/.test(location.hash)) {
        less.watch();
    }

    if (less.env != 'development') {
        try {
            cache = (typeof(window.localStorage) === 'undefined') ? null : window.localStorage;
        } catch (_) {}
    }

//
// Get all <link> tags with the 'rel' attribute set to "stylesheet/less"
//
    var links = document.getElementsByTagName('link');

    less.sheets = [];

    for (var i = 0; i < links.length; i++) {
        if (links[i].rel === 'stylesheet/less' || (links[i].rel.match(/stylesheet/) &&
            (links[i].type.match(typePattern)))) {
            less.sheets.push(links[i]);
        }
    }

//
// With this function, it's possible to alter variables and re-render
// CSS without reloading less-files
//
    less.modifyVars = function(record) {
        var newVars = "";
        for (var name in record) {
            newVars += ((name.slice(0,1) === '@')? '' : '@') + name +': '+
                ((record[name].slice(-1) === ';')? record[name] : record[name] +';');
        }
        less.refresh(false, newVars);
    };

    less.refresh = function (reload, newVars) {
        var startTime, endTime;
        startTime = endTime = new Date();

        loadStyleSheets(function (e, root, _, sheet, env) {
            if (e) {
                return error(e, sheet.href);
            }
            if (env.local) {
                log("loading " + sheet.href + " from cache.", logLevel.info);
            } else {
                log("parsed " + sheet.href + " successfully.", logLevel.info);
                createCSS(root.toCSS(less), sheet, env.lastModified);
            }
            log("css for " + sheet.href + " generated in " + (new Date() - endTime) + 'ms', logLevel.info);
            if (env.remaining === 0) {
                log("css generated in " + (new Date() - startTime) + 'ms', logLevel.info);
            }
            endTime = new Date();
        }, reload, newVars);

        loadStyles(newVars);
    };

    less.refreshStyles = loadStyles;

    less.Parser.fileLoader = loadFile;

    less.refresh(less.env === 'development');

// amd.js
//
// Define Less as an AMD module.
    if (typeof define === "function" && define.amd) {
        define(function () { return less; } );
    }

})(window);